Ha Ha Ha Ha!
Just fucking with you. Seriously though, I do have some advice because I've been in the exact same situation as you at an age very close.
I dated the girl I lost my virginity to for about 3 years, and eventually her sex drive went the way of the dodo. I expressed my feelings and she never made an attempt to make things better. I was always pissed at her because basically what she was saying was, "You're not worth the effort". So I broke it off. Soon after I started dating someone else, someone a lot more experienced (with different people). You know what? The sex was the best I've ever had, and she was impressed by what I could do. She said it was because I had dated the same person for so long, I had sort of an in-depth experience.
So don't worry about not being good enough. You may be better than you think. Just be safe, and don't jump in to it.
Now for lesson #2.
You've been on the sexless wagon for a while and this new relationship will be a little clouded by this. Take it slow, and don't assume that what you think is love is love. Remember how it was in the beginning with your ex?
With me, my ex must have thought I would never date anyone else, and when I did it changed her a lot. Suddenly she wanted to have sex a lot. And we did even though I was dating someone new. Eventually, my new relationship ended and my old one started again. A few months down the line and guess what? No sex again.
Eventually we broke up again, I dated and moved in with someone else, so my ex changed yet again and the sex with the ex started again! So my newer relationship ended and I got back with the ex. Eventually we got married, and a few months into it and guess what? No sex! (Yes I know I'm a moron)
The moral of the story is, your ex-girlfriend may sober up and act like you want her to get you back, but don't fall for it. Learn from my mistakes pal, and just keep on dating. Girls like that NEVER change, and there are plenty of girls who have normal sex drives, or care enough to get help if they don't. Enjoy your youth and never look back. Oh and don't forget girls with lots of ecperience can have lots of STDs! (Made that mistake too)