Talk to Urologist on Masturbation And Penis Size

Dear Doctors, i have a serious question. I am 26 and single. I have been masturbating for a long time, since i was a kid (13 yrs old). And i am addicted to it and porn. Some time back i used to masturbate about 5 times in a week and now i masturbate once in a week. The problem is now i feel very lazy and weak, my knees some time pains, just after masturbating i feel dizzy all time. And the big problem is my penis size is very small. I am very worried. Now i have realized that its all because of masturbation. So how can i gain my penis size its only 3 inches in length when erected and 1.5 inch in girth. What do i do now. My marriage is planned at the end of this year. I am very worried. Please suggest me what to do now