alright, this is only a guess, but maybe they just started dating and he really likes the girl, but then he found out something about her(like maybe she's secretly kind of a whore?) that shows him the relationship isn't going to last. So now he's kind of pissed that he started something with her and he wants out, since she's not ready to comit to an actual relationship. As for the chorus, i think by "doing it" he means being typical high school cliche and just staying with her, even though they both know it's just sort of a meaningless sex fling
alright, this is only a guess, but maybe they just started dating and he really likes the girl, but then he found out something about her(like maybe she's secretly kind of a whore?) that shows him the relationship isn't going to last. So now he's kind of pissed that he started something with her and he wants out, since she's not ready to comit to an actual relationship. As for the chorus, i think by "doing it" he means being typical high school cliche and just staying with her, even though they both know it's just sort of a meaningless sex fling