Very confusing situation... long story, real question. any real help will be greatly appreciated.?

hokay so.... theres this girl that quite frankly, i believe i love. cant stop thinking about her and she is, at this time in my life, one of the few things that can actually make me smile. i am a sopre in highschool and she is a junior. at the beginning of the school year, i had known her for a year and i liked her during the previous year but i made no attempt to get closer. this year that has changed and i am doing everything in my ability to get to the point where i can ask her out. after about three months of getting closer to her i asked my best freind (he had been friends with her since he was young) out of desperation, to call her up, ask if she thought i liked her and what she thought of me (he pretended he had no idea). she said she thought i did like her and that at that time she only liked me as a friend. now, a month later, i have been talking to her pretty much every day. both in person (on the bus everyday) and on aim. she has been opening up much more to me and every once in a while she will bring up the fact that she thinks that she is fat. now, i know that this is a big load of bull so i always just explain to her why she isn't and i just try and comfort her. recently on the bus she has seemed to become much more shy. i normally have to keep the conversation going, but recently it has been like pulling teeth, not to mention that i am shy on my own and find it extremely difficult to do it in the first place. when i get off the bus and i say bye, she says bye as well but on her face is a look of either disappointment or something else, i cant tell. keep in mind though, i have still been talking to her on aim with little difficulty pretty much every day. now i have no idea what she feels about me. whats going on in her head and whats going on?