It's disputed whether there is such a thing as sex addiction, as the BBC's Sangita Myska explained a week ago. But she has interviewed many people whose lives have been severely affected by compulsive sexual behaviour - including one woman who discovered by chance, after 20 years of marriage, that her husband had a secret life. This is an edited transcript of her story.
I always thought I had a very normal marriage. We'd been together a number of years before we got married and we'd been married for a couple of decades and had children. My husband was a successful businessman, who travelled a lot for work so I spent a lot of time on my own bringing the children up but he came home every weekend. I just assumed it was a very normal relationship. He always seemed happy when he was at home. I had no inkling of what was going on whatsoever.
Then one day I had to pop into his study to find something on his desk, and his laptop was open. I'd never checked up on him, but the screen was on his emails, and I saw an email that showed a reservation for a hotel in London, for the day after I was leaving to go on a holiday with some friends. I thought, "That's a bit strange, why has he got a hotel room booked?" It just seemed odd. I couldn't understand it.
I sat on it all day and thought about it. Later, when I was lying in bed, I just couldn't get it out of my head. So I plucked up the courage and asked him why he had a hotel booking. And he didn't reply.
The silence told me that there was something dreadfully wrong. It seemed like forever. After what felt like half an hour - I suspect it was probably more like two minutes - I got up and I said to him: "What's going on?"
I can't remember his exact words but he just said he was sorry and that he was seeing somebody - at which point I grabbed my dressing gown and went downstairs. I just couldn't stay in the same room. And I cried.
Eventually he came downstairs and sat opposite me and told me how sorry he was. He told me that he'd started going to strip clubs a while ago and had met a dancer at the strip club who he had become close to and that he had booked the room to meet her, in order to take the relationship further.
So I asked him there and then whether they'd had sex and he told me he hadn't, that at this point in time there had been some "teasing" but nothing more than that.
I wanted to believe him. I think I was absolutely desperate to believe him. I was dreadfully upset but there was a little bit of me that thought, "OK, we can, we can sort this out. This is just a middle-aged man, a moment of madness. We'll, we'll get through this."
And because my friends were desperate for me to join them on our girls' weekend I thought I would have a few days away from him to give me time to process my thoughts.
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I didn't tell my friends. I wanted to keep it to myself. It was a really really difficult few days. I didn't sleep very well at all. I couldn't eat. Looking back, I'm not sure quite how I got through it.
When I got home, we talked a lot. There was a lot of crying on my side.
But the truth is, I always felt it was far too coincidental that I should just happen to come across an email of a hotel booking before any sexual relationship had taken place. It was just far too much of a coincidence.
So I pushed him to look me in the eye and tell me he hadn't had sex with this woman, which he couldn't. This is probably two to three weeks after I found the email. Then he admitted that there had been a sexual relationship and that it had been going on for a few weeks, or a few months.
I'm looking at this man I've known for all these years thinking: "How could you have hidden it? How could I have not have realised anything was wrong?"
I couldn't understand how the man I knew had done what he'd done, had got himself involved in something that just didn't ring true to the person I knew. None of it made sense so I went shopping for pain. I basically started looking through all his emails.
I found other hotel reservations that dated back further than the dates that he'd given me. And after going back several months and even a couple of years I found that some of the dates didn't match his story of how long he'd been seeing this woman at all.
The turning point came one day when we went out for a walk. I just said to him, "I have to know everything. I'm going to keep pressing and keep pressing because I don't think I know everything." I threatened to look at bank statements, threatened to look back through all his emails. I told him that I really needed to know the truth.
And he said to me, "Are you sure you want to go down this route?" At which point I thought, "Oh no, there's so much more to this." But I had no idea what he was going to say would be quite as devastating as what then came out.
He had been using prostitutes throughout our marriage. He also told me that he watched a lot of porn, sometimes for hours at a time. And that he went to strip clubs, and sex clubs, and sex cinemas while he was travelling abroad.
I didn't tell anyone. One or two friends noticed that I was quieter and asked me if I was all right but I always had an excuse - "I'm tired, I'm not sleeping very well, must be the menopause or my mum hadn't been particularly well."
I was ashamed of what had happened. I wondered what people would think when I told them, what they'd think of Dan, what they'd think of me. I assumed people would judge our marriage and think it was a sham marriage. I also felt people would think I hadn't been good enough for him, not pretty enough, not sexy enough.
I've always been a relatively confident person. I wasn't the sort of woman who had her nails done every week or had botox. I'm middle-aged, I'm a little bit overweight, I'm getting old, I've got wrinkles but I thought that was just normal for my age. But this completely shattered my self-esteem. I questioned whether I was a fun person to be with.
I started wearing more make-up and making sure that I looked as good as I could. I had already lost some weight - it took me quite a long time to really want to eat anything. I bought some new clothes, had my hair done more often, perhaps, and I did go and have some botox.
But I also believed there was something wrong with him in his psyche - some illness. I thought he needed help, and that he needed help from me.
When I went along to the clinic, and it was explained that his behaviour was probably the behaviour of a sex addict, I believed that. I thought, "Oh great, there's a label, that's it, he's ill. There's something wrong with him."
I want to believe that because then I can keep reassuring myself that "No, you had nothing to do with it, it was always going to happen."
But he came back from a counselling session once and said he wasn't certain it was a sex addiction or whether he had just made bad choices. I found that very difficult to hear and it did affect me for a couple of days.
When we started marriage guidance, one thing I very clearly remember him saying was that life before I discovered the truth was like being in this dark tunnel holding the secret and hiding it and lying - and now he could see the light at the end of the tunnel.
And I remember looking at him and thinking, "That's great for you but I'm the one now living in complete darkness. Everything for me is now dark and gloomy, and I'm holding the secret now because I can't tell anyone what's going on." And I felt that was just so unfair.
I don't want to tell people because I don't want people to judge me. For example, I was watching the Ryder Cup the other day and seeing Tiger Woods with a girlfriend and thinking people would be looking at her and thinking, "Oh that's the little woman, the doormat. He probably treads all over her. You know he's the sex addict, he doesn't have respect for women." People judge people. They assume they know.
In a lot of ways our marriage is better than it was, which seems like a crazy thing to say but we spent months going to marriage guidance. We are much more open with each other. We talk a lot more and we actually talk about feelings, not just what we've been up to today or what we plan to do. We actually talk about feelings, both the good and the bad.
There are still quite a few occasions where I do get low but I would say most of the time now I feel that our marriage is on an even keel and my emotional state is on an even keel.
Can I forgive him? This is something I've talked through with therapists and I don't really know what forgiveness is. I don't think I'll ever forgive him for the hurt he has caused me, it's so deep. I don't think I could ever forgive that but... I want to be with him and I do love him. And life is good with him. Is that forgiveness? I don't know.
I think at the end of the day we're good together. We're good friends. I still love him, and he assures me he still loves me, that he always has loved me.
Also I'd hate for my kids to know, absolutely hate it. I think they'd lose all respect for their father. And my family adore my husband. I think if you met him, you just wouldn't believe it. He's just not the person to do something like this.
He would be the last person I would suspect of doing something as stupid as what he did.
This is an edited transcript of an interview that features in the Addicted to Sex podcast, with Sangita Myska, produced by Sarah Shebbeare
All illustrations: Karen Charmaine Chanakira for the BBC.
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The BBC's Sangita Myska has been meeting people who say they've suffered from sex addiction, in order to understand whether it really exists, and if so, what it is. Here two of them describe their problems - a woman who started watching porn for hours every day, and a man who bought sex "like pizza".