first (serious) crush on a girl..HELP!

i've never written in one of these before so bear with me.

there's an essay of things to say about what i'm going through right now but i'll try to keep it short.

i'm a teenage girl. i just switched schools. there's this girl at my new school. she's not very feminine or masculine, just kind of boyish and edgy. she's not beautiful and more cute than pretty. but there's something about her. i'm totally attracted to her, as a person and physically. i've never liked a girl before her, and i'm still really attracted to guys in general. but i can't stop thinking about her. i've thought about kissing her, and even being in a relationship with her. i don't even feel uncomfortable or weird when i think about it like i do when i try to imagine being with any other girl. we've been in the same class for a while, but it wasn't until last week when i started talking to her more that i realized how much i like her. which was about a day before i found out she has a girlfriend.

alright, i'll back up. she's friends with this guy, who i'm starting to be friends with too. he's like our link. i don't really talk to her when he's not around because i'm too nervous. i've been talking and hanging out with them around school more in the past week. she laughs at things i say, and sometimes i feel her looking at me in class. i don't know what the looks mean. does she like my necklace? is she wondering how i do my hair? does she think i'm pretty? does it just not mean anything? why is she looking at me??? it's just as aggravating to like a girl as it is to like a boy. you really don't know what anyone is thinking.

anyway. we're definitely not very good friends yet. i mean, we're not even friends on Facebook at this point. and i don't know what i would say to her if we were alone. but i'm getting to know her better. it feels like there's some tension between us. not a bad tension. just a tension. i have this fantasy that it's because she's actually really attracted to me and is trying to hide it because she has a girlfriend. but that's probably not it. right? or maybe it's just because i'm really awkward. i make a lot of jokes when i'm nervous. like, a lot. it's just hard for me to be myself, i guess. i'm super self conscious, whether it's around someone i like or someone i just want to be friends with. but that's a whole other issue.

obviously it's impossible for me to make this really short. but trust me, it could be longer.

here's what i know about her relationship. her girlfriend goes to a different school, but i think they still see each other outside. i don't know how often. they've been together less than a year. the girl i like has had a couple girlfriends (and boyfriends) before. and that's all i know.

basically what i need is help. advice. what do i do? i've only liked her for a week but it's driving me crazy. i'm, like, obsessed. and i have no idea how long she's going to be with her girlfriend or if she's even interested in me/if she would be if she was single. i really have to do well at my new school and i can't afford to get distracted, which i'm bordering on right now. and what if she breaks up with her girlfriend? or what if she's interested or becomes interested in me while she has a girlfriend? obviously i wouldn't force myself on her when she's with someone else. but if she were to approach me i don't think i could turn her away. but how would i let her know that i'm interested in her too? i definitely don't give off a girl-liking vibe. what if she would want to break up with her girlfriend if she thought she could be with me but doesn't think i'm into girls? but i can't act interested in her while she has a girlfriend and while i'm not sure if she would ever like me. it's all so confusing and frustrating. i have no idea what to do. i'm hesitant to just give up this feeling entirely. this is the first time i've liked a girl, and a big part of me really wants to see it through. i've only liked one other person (a guy) this much. what if this is the last time i like a girl? i might never know what it's like to be with one. and even if i wanted to stop liking her, it's not like i can just ignore her, especially if i want to be friends with her friends. and i definitely don't want her out of my life as a person. i know what i feel is real, albeit intense for someone i don't know that well. but it's also more confusing than anything i've ever felt. am i crazy? am i thinking way too much into this? i just really need help. any advice would be appreciated.