Skin disease on hand leg, knee

I had started masturbation when I was 7 year old only. At that time no ejaculation there but I felt happy by doing this. I started playing with my private parts since I was 5 year old and finally I started masturbation when I cross 7th birthday. After some time white patch appears on my left knee. I thought this happen by my masturbation so I stopped that it disappear from there. But when I cross my 11th birthday ejaculation take place by night fall. And again I started masturbation because I felt started enjoying. I don't know but I can't stop it. Main problem is that when I stop masturbation my white patches became very light and when I used to 3 or 4 times in a day it became very white and started increasing. It happens after sex too because ejaculation in that process also. Please suggest me I told this problem with my doctor but he refused and said it's not like that, that is another thing. Please help me...please.