Need some help...

So yeah, I'm in high school and there's this girl in another class that keeps driving me crazy. I used to be a gamer, but over the last couple of days I've lost my will to play anything. I used to play world of warcraft. Don't want to play that anymore. I used to be a tough guy at school, but now, everytime she's around, I keep feeling this urge to be good and behave. Also, I used to eat a lot. And I mean A LOT. But since Thursday, when my feelings really started to grow (she's been around since September), I can't get a decent meal through my mouth. I keep feeling sick whenever I smell or see food. Also, I was a funny guy. I kept making jokes in class, and we all laughed our (put obvious word here) off. But I've totally lost my sense of humour. Pretty much all I want to do is listen to the beautiful piece called Aerith's Theme from Final Fantasy 7, played by Arkton, and think about her all day long. I have this really good friend that I talk to and that helped a lot, but this can't go on like this. Classmates keep telling me that I've been acting like a zombie. The answer may seem simple: go talk to her and flirt. However, my friends made this a whole lot more complicated than it's supposed to be. Like today, they told the girl that I've been feeling depressed. Now she feels sorry for me, which really isn't a good thing to start off with...right? This is kinda where I need your advice. I know, I seem selfish to ask for help and give you nothing in return, but I'm desperate. I want her attention. I want her lips. Don't think I'm a sex addict looking for a hump, because honestly, sex is the last thing I have on my mind with her. I don't know if this matters but I'm 16 so...if it's worth anything, you know my age. You should also know I'm very shy. Too shy for my own good. I can barely find the nerves to look at her when nobody's around. Now what do I do?