Why would i feel this way?

ok, well.... lately i have found myself, well. flirting with guys. three different times i was out with Friends or something and id see a guy. i would look at em then hed look back. id wink at him. he would smile. i wouldn't/nor would i let him take it any father then that. this feels weird because i thought i was into girls. it gets a little more complicated though. i have been asked out by a couple girls. i always sed no, and i blamed the no on that i have a thing with a different chick.. but i never take it to the next level of actually dating. i don't know why though. i am extremely confused on this. im i gay because i am starting things with different guys, and not going out with any girls? am i Bi because i want to go out with a girl, and starting things up with guys? or am i strait because i don't take things any farther with guys, but i will with girls? i am really worried about this and need some advise plz!