Why have i lost interest in guys?

hey im a 'straight' female 19, I recently fell in love with a friend of mine (female) and still crushing on her after a year! really hurts me that its unrequited love, but I'm still not giving up as we both seem to be bi-sexual and have started going to gay bars and having sexual flings with other girls, plus me and her kissed a ton of times since we've been going to gay bars, she's the first girl i've liked, and i'v seen a few more that take my liking, but I am in love! would do anything for this girl, never thought I could be a lesbian as i've had sex with guys (haven't yet had an enjoyable experience) now heres the thing guys do not interest me I quite alot get that arghh hate men feeling, its like when a guy trys to get with me I want to say no, don't want them to think im frigid its simply because it doesn't feel right, I have been in love with one boy once when I was about 13..first love relationship for over a year, haven't had a relationship since, now I don't want to tell people I'm fully lesbian (just in case it isn't for sure if ya know what i mean, I dont want to go labeling myself, but I wan't to know to myself I don't even know why this is happening, can you stop liking guys and turn lesbian (once straight before)?