Hello Doctor, I Have A Habbit Of Masturbation 10 Or

Hello doctor, i have a habbit of masturbation 10 or 12 times a week, and am going to very thin, losing my weight. My penis is looks like thin, when erected it is 4 inch, is there any problem the size of penis?. And upper skin when it is normal the skin forward and back going, but when erected, upper skin little go back, and it is very tight to corona of penis, what is the solution for that