A hospital worker said she was "lucky to be alive" after it took five years to diagnose the "time bomb" of a heart condition and cancer.
Bethan Goodey, 27, dropped from a dress size 10 to a four while continuing to work 12-hour shifts at West Suffolk Hospital in Bury St Edmunds.
Prior to a stage four tumour being found in her chest, she was regularly lifting patients and heavy equipment.
She said people did not believe how ill she was because of her age.
Ms Goodey's weight fell to 7st 5lb (47kg) - and she was told by friends she may have an eating disorder - before a routine chest X-ray for a persistent cough revealed a 4in (10cm) cancerous tumour in her chest, which was causing fluid to build up dangerously around her heart.
Ms Goodey, from Bury St Edmunds, who is currently shielding, said: "I'm very lucky to be alive as I was walking around with a ticking time bomb inside me.
"It's so scary when I think how close I was to dying and I had no idea.
"After years of unexplained weight loss, going back and forth to the GP, each time being reassured that I would be 'more unwell if it was anything serious' or that my bloods would be 'more deranged' if it was cancer, I was finally diagnosed with the cancer."
Her condition was so severe that she was told not to move due to the risk of her heart failing, and was wheeled to the hospital's cardiac unit for monitoring ahead of surgery.
Ms Goodey underwent six rounds of chemotherapy over seven months at West Suffolk Hospital and had heart surgery at the Royal Papworth Hospital in Cambridge before being given the all-clear in March.
She said it had "taken ages" for her to "trust" her body again after her condition, but she is now urging people to join a Cancer Research UK campaign to walk 10,000 steps every day in March to support the charity's work.