Please HELP: Boy Trouble!!!?

i feel like im in an akward position. I like guys. I really do. i spend most of my time fantasizing about them. I REALLY DO!! I am a seventeen year old high school senior, but have never been kissed or even had a boyfriend. I feel like boys just dont notice me. well, the first boy i ever liked was a white guy, then i liked hispanic boys, then black guys, then asians, and then for a while it was damn near everything that moved!!! now i find myself infatuated with white guys. I myself am a nigerian-american girl who, i guess, is just looking for some kind of love. Anyway, there is this guys, a white guy, who i am absolutely nutzo about, but he has a girlfriend. Can i still flirt with him? Is it wrong to fantasize about him? Is it wrong to fantasize about so many guys in general? Is it wrong to fantasize about teachers? I just want to know.