I don't feel anything when pleasuring myself

So I'm really scared guys I'm 13, and I have been masturbating for a year, we'll not really masturbate , what I did is just turn on some porn, try to fap, then my penis will itch and I would stop , this lasted for 30 sec or so, I tried going slow too, but it didn't work! It doesn't matter what I do, when I masturbate I don't feel any sensation at all ! I'm scared to death that I will never have sexual pleasure , even when I'm super turned on and I masturbate I don't feel anything! What should I do? I tried in the shower with the shampoo but no luck either The only technique that DOES WORK is really weird I do it in the shower ONLY and I'll tell why ; first of all I'm circumsized ( if that matters ) and when I'm STANDING in then shower I rub my hand palm AROUND THE HEAD ( tip ) of the penis and i get a muscle spasm and I almost fall cause my legs feel weak, after I stuck the muscle spasm stops too, but when I do this techniquie, I REALLY have the urge to pee, so when I circulate my hand around my penis head, I feel the stream of pee coming and then I pee What should I do? PLEASE HELP ME