I masturbate before I go to sleep at night. Usually nothing is wrong, but (and this always occurs at night, I ve found) after I masturbate, a few minutes,my scrotum usually gets very tightened up, and there is painful feeling above my crotch.and when i urinate there is a blood on my urine but painless and..Usually I just sit there, drink some water until the feeling goes away. ANY idea what this is?