How To Prevent Sperm Leakage While Sleeping?

Hi,I am 25 years old. I having this sperm leakage often during sleep. I was masturbating daily for a year. But for the past 1 month i didn't masturbate but somehow it comes out in sleep. Please help me to get rid of this. I am doing exercise daily, running for half an hour with some workouts in gym. Still I am unable to stop it.