Hi, I am 28 year old virgin guy, I used to masturbate alot in porn way for long time. But, now I have stopped doing it in porn way but once or twice I masturbate before taking shower. I think due to so much jerking, my penis shaft gets thin from middle and I can also see some red around black line and spot on middle of penis. I also get pain in my penis for 5 seconds once or twice in a day and sometimes after couple of days and sometimes after a week. I ll be very grateful, if you can let me know what can be the problem. Thanks