It doesn't seem likely that steroids can interrupt the testicles development. You should perform a spermogram and request a blood testosterone level examination to check if your testicles are functional, or not. Even if you have small testicles, they are probably not the reason for premature ejaculation. Premature ejaculation is a functional disorder without any structural (organic) damage. Fluoxetine is an antidepressant that can be used for treating premature ejaculation. It needs a few months to start acting.