I feel so used

Motherfucker, motherfucker, motherfucker. Motherfucker.
Okay, so, this guy that's flirted with me since I was about fifteen (three years, btw) came over last week, we flirted, and it ended in drunken sex (I know -- it's awful).  Well, I come to find out today that he has a girlfriend.  And he loves how beautiful, and sexy, and wonderful, and amazing she is.
I am so upset.  I feel used and violated, and like a slut.  I am not a slut.  I know, my decisions were not the best.  But still -- I'm not a slut.  If he had told me, "Hey, nothing will come of this," or "Hey, I just think you're hot and I wanna bang you," I think I'd feel somewhat better about all this.  Maybe.  But to just lead me on and to fuck me while I'm completely wasted is just uncalled for.  And then to have a girlfriend a week later?! I'm so so so so frustrated.  I'm so hurt.  I don't know what to do about any of this.  What the fuck.