Telling a boy

I really really like this guy and we’ve only hung out 3 times but our sexual connection is so strong I’m going to be honest and say i do want to have sex with him.. i haven’t had any sexual feelings for anyone after being diagnosed bc sex just felt scary. I know i can’t have sex with him without tell him because even if i never get outbreaks anymore i know that there’s always a possibility. So how do i tell him ? I don’t want to scare him off or be rejected (biggest fear) i just don’t even know what to say I’ve never told anyone... I’m so scared and i hate how this can make or break future relationships it’s so fucked up