Q: When I masturbate my “balls” pull up inside my body right before I “come” and it kind of hurts.  I was wondering if this could be an STD or a problem or what. They don’t go all the way up inside my body; they just pull up-like out of the ball sack.

A: What you are describing is a completely normal part of the male sexual response cycle as described by noted sex researchers William Masters and Virginia Johnson.

As sexual tension mounts, the testes (“balls”) normally elevate and begin to rotate forward so that their back surfaces rest in firm contact with the perineum (the area between the scrotum and the anus).  Full elevation of the testes indicates that orgasm is going to happen very soon.

Your discomfort may be normal as well.  During sexual excitement, body tissues and organs become filled with blood.   This engorgement can feel somewhat uncomfortable, which may explain why it hurts for you during masturbation.  If you find the pain grows worse, or happens when you are not aroused, get checked out by a medical provider.