I masturbate very often and have a long stamina, when I'm at home and have nothing better to do my sessions usually last an hour or longer. Yesterday I had multiple long sessions, and sorry to get into detail, but I'm very concerned, while masturbating at one point I remember having my hand come down and hit my testicles repeatedly. It didn't hurt, in fact it actually felt kind of good, it wasn't hard or anything. Anyway, today I realized that my testicles are huge!! Definitely swollen, I noticed when I went to masturbate and got concerned. When I tried to masturbate I couldn't get hard but it may have just been from being worried, I also didn't try for long since I was so scared.