how do you improve something that is nearly gone or totally gone?

I openly admit to not being a good lover for my gf and it SUX and its hard to admit. The size is fine, but the duration is not. She is my first and only and been doing it for 4 years. It has NEVER been good. At the beginning she was patient, hoping with time itd get better, well instead I got HUGE and it never got better, only worse. Now, im the healthiest and best looking ive ever been, and still duration is minutes long. She is totally dissatisifed to the point of not wanting it anymore, at all, and not even offering it cuz of how much she hates it. I dont initiate it, ever, knowing how much she hates it. Our foreplay is NON-EXISTANT because she said i wasnt "good at going down" and yet, we only tried it maybe 10x in our first year of dating. I dont have the experience or the answers as to how to build up our sex life. She can be a freak and has/had a high sex-drive, used different outfits, and talked dirty, but now its all gone. She has added stress and depression OUTSIDE of us but i know that the lack of sexual passion is still a huge issue.

HELP!!!