I'm in a bit of a crisis right now with my ex-girlfriend...?

I am a senior in my high school, and I am really going through a tough time right now. I met this girl at the beginning of the school year, and she is a freshman, and when we started to talk more ofter to each other, we got really close (I mean in a friendly way) and eventually I started to like her a lot. I found out that she had the same feeling for me and I asked her out on December 19, 2008, and we dated for a month until she broke up with me on January 20, 2009. I did not take the break-up very well because I have been feeling sad, lonely, and depressed for the past 2 months, and I just can't seem to move on with myself. Every day, all that comes to my mind is my ex-girlfriend, and that is all that I think about pretty much all the time. I am very depressed because we are no longer together, we don't talk to each other (we only talked twice since she broke up with me), and I am sad that our friendship is now not the same anymore. I really cared for her a lot, and I don't understand why she left me. She was my first girlfriend, and throughout the time we were dating, I always hugged her and cuddled with her, but I was just too afraid to hold her hand and kiss her because I did not know how to make the first move. The day that I was going to kiss her was the day that she broke up with me, and I am saddened that she left me. She told me that she was "emotionally unstable" and couldn't handle being in a relationship because she really viewed everyone as only a friend, but that is what really hurts me. Every day now, she doesn't approach me to talk, she walks right past me like I don't exist, and she basically ignores me (although I have been doing the same thing). Our friendship is ruined, and I don't know what to do. I feel like it's time to start talking again, but at the same time, it will just feel awkward to me. I asked her back last month, but she rejected my feelings for her and wanted to be single instead. I have been acting out in anger and rage, I've become more of an to people, I am so depressed that I am trying out drugs to relieve the pain, and it is because the break up has made me into a different person. I still have feelings for her, but I am too afraid to talk to her because I don't know how to approach her anymore because I see that she seems to be a lot happier without me in her life and got over me in a matter of days. I want her back, but I know that I will get rejected anyway, so **** it, I don't know what to do. I really don't give a **** about my life anymore. All that will practically make me better is if we got back together. What should I do? I really need serious help because I am losing myself and I don't know what to do. Please.