Men - Confessions

Im 20. I am deeply in love with my girlfriend and have plans to eventually marry her. Call me too young, everyone else has.
My name is Jason and I'm afraid of destroying this relationship with her through my addiction to not so much pornography but masturbation in itself.
Her and I don't have sex nor do we really do much more than kiss most of the time so a sexual release is not available in an appropriate way or so I think. For years I have just "done things myself" so this pent up sexual pressure didn't really exist.
I feel incredibly guilty every time I do it. Its been about 12 months of dating her and I think Ive promised myself I'd quit at least 100 times. I need help finding a way to permanently quit. I want to and need to but somehow always end up in the same spot Ive wanted to avoid for a super long time.
If anyone has any advice or anything to give please do.
I cant even really make myself try to quit. Once I get going I begin to ignore God tapping on my shoulder and just do it anyways...

Thanks for all your help. I want to do this so that my life and relationship with her can be pure and honest.

Thats what I want and need.

Thanks a lot.