Calcium build-up. Either that, or you eat styrofoam beads. LOL Just kidding. You lift heavy weights? That may cause the calciums in your system to build up, and exit the anus region, or sometime painfully, THE PENIS. I had that peeing problem. Peeing strings of calcium! Ouch! No more lifting twice the weight of my own any more! Drink at least a liter of vinegar twice in one day. See what happens.
Be easy on potassium too like in energy shakes, drinks, bananas, and so on. Take a care, and no masturbation, which the prostate may effect the problem and make it worse.
~ Johhny