Can a doctor know if you have masturbated?

Why do you ask?: If a man uses a tight grip in the same place most times, it may produce a faint mark. Beyond this, why do you ask? Essentially all men and most women enjoy their bodies after puberty, and if anyone tells you this is unnatural or wrong, they're trying to alarm you for their own dark purposes. Your doctor knows this. He/she doesn't care. It's your body. Talk with somebody reasonable -- maybe dad.

Not usually: This does not usually leave any findings on a regular or genital exam.The doc wouldn't care anyway, since it has nothing to do with your overall health.