how can I stop semen leaking, i think it's because of over-stimulation

I was doing over masturbating 3-4 years.. now my penis not getting hard and and from 3 years when ever I think of sex or talk or chat with girls on phone my penis leaking. (Dhant problems) also sometime when i pee some semen comeout.I think my nerves are become very weak to stop leaking semen.Semen also become very thin. I ejaculate with in jst one minute . So plz tell me how can I cure this problem...