Premature Ejaculation Problem. Back.

I'm male, 22 years old. I have been masturbating from last four years. When I did it for first time I really liked it and continued. I did it for 3-4 times per week. In the starting stage, I had good erection and ejaculated good amount and quality sperm but from last one year I'm unable to have a good and strong erection and sperm is like watery sometimes. I'm ejaculating within a minute and sometimes within 20-30secs, if I masturbate fastly. After ejaculating it is taking more than 1-2 hours for erection. If it's erected within 1 hour my penis is paining very much. And one more thing, I think my Penis is uncircumcised penis. The head of the penis is covered with foreskin. I'm unable to push it back, it's so tight to push back.