Could Premature Ejaculation Be Due To Excessive Masturbation?

I used to masterbate from 2007. After that I did it for many time.. May be al most everyday. But Now If I be with my Girlfriend. After I kiss or foreplay I get clear fluid in my penis and my penis becomes less harder .. So what Can I do with This problem. I have decided to stop masterbation. And watching porn movies. Anything thing else please give me some suggesion Dr.