Sean, dude, I hope you're not being serious. Causing yourself harm is NOT the answer to this. That 'one girl' or not, she's not worth that sort of thing. Go to your room and scream; beat the stuffing out of a soft object if it helps. You can't control how the girl feels, and inflicting harm on yourself isn't going to change that. All you can change is how you deal with it. Take your mind off of her, please. You're still a kid, and you have years to meet new people. I know how it feels to not have the 'one girl' you want, but... NOTHING is worth intentionlly hurting yourself over.

Definitely praying for you, man...