Hey Flasken,
Sorry to hear that you're having girl-related issues. I'm sure most of us have been there and know exactly what you're feeling. I know its quite cliche to say it, but drinking won't make your problems go away.
I'm not entirely sure what you feel when you drink, since I've never had a beer [or more than a sip of someone else's cocktails..], but I'd suggest this: Similarly to stallion11msu's suggestion to go running, go somewhere quiet... A few years ago when I was having similar problems, I jumped on my bike and didn't come home until several hours later. With nobody to distract me [the occasional pedestrian excluded], this gave me time to think about what was going on, and what to do about it. In a nutshell, find somewhere or something to do that's comfortable and that you don't need to concentrate hard on what you're doing. Take a walk/job around the block. But instead of trying to drink it away, do some thinking about the issues involved. While it may hurt to dig deep for the true answers, it may save a bucketful [or more] of hurt feelings later.
This, and whatever the issues are, don't jump into anything too short-sightedly. [Unless, of course, that's what you're looking for.] Especially at your age, there's much more to life than girls. You're young.. go enjoy life with your friends. Like braillediver said... "Women do strange things for apparently no reason." I can vouch for this... and you should really just enjoy life without needing to submit to the whims of a female.
Additionally, if you're not sure about something, don't commit. This is from personal experience. You'll save everyone involved hurt feelings later on.
Anyway... that's just my $0.02 worth...
Good luck with the girl, by the way.