World number one Andy Murray can find "no reason" for his "struggle" with form following defeat in the second round of the Italian Open.
The 30-year-old lost 6-2 6-4 to Fabio Fognini in Rome and has now won one title from eight events in 2017.
The French Open begins on 28 May but Murray has only reached one semi-final in his last four clay court events.
"I'm just not playing good tennis and need to try to work out how to turn it around," he said. "I believe I will."
He added: "The last couple of weeks have definitely been a struggle and a long way from where I'd like to be. There is no reason for it from my end.
"Movement the last two weeks has not been good. My movement has been a big help, the last couple of years, but certainly the last couple of weeks, that's been a problem."
The Scot insists his difficulties are nothing to do with the pressures of being world number one.
But he admitted he found it hard to create chances against world number 29 Fognini, as he suffered a fifth defeat in 10 matches.
Murray's last title came in Dubai in February, a contrast to the form he showed in winning five events in a row to end 2016.
He will arrive in Roland Garros - he was beaten by Novak Djokovic in last year's final - with his run to the semi-final of the Barcelona Open in April as his best return on clay in 2017.
Since that loss to Dominic Thiem, he has gone down to world number 50 Borna Coric at the Madrid Open before a straight sets defeat by Fognini.
Ivan Lendl - who coaches Murray on a part-time basis - will join up with the team later this week for the grand slam event in Paris.
Murray's ranking under threat? - analysis
BBC Sport tennis correspondent Russell Fuller:
Andy Murray will be the world number 1 during Wimbledon, but will have to play exceptionally well if he is to remain at the top come the autumn.
That is because tennis' ranking system is calculated on an annual basis, with players defending points they won in the same week the previous year.
Murray has shed a significant number of points by losing early in both Madrid and Rome, as last year he was the runner-up in Spain and the champion in Italy.
He has nearly 4000 points to defend at the French Open, The Queen's Club and Wimbledon, and an even greater number in October and November - the one down side of winning his final five tournaments of 2016.