I let the only thing I had go.

I just got out of school for summer, I was in my junior year. I have social anxiety and don't really have any friends and I've never had any sort of relationship with a girl. I'm very lonely and had depression from this. First semester around October or November a girl in class starting talking to me, her goal was to get me out of my shell and she did, we'd talk non stop in class. In January, we got each other's phone numbers and everything went from there. We texted all day everyday. We got really close and started dating. She was my first for a lot of things. Like sexual things and the first person I ever opened up to and told my feelings. We started dating in February for about 3 weeks. We truly loved each other, but I just didn't see us together. In the break up I came off as racist (I'm white and she's black). I really hurt her but she truly loved me to and eventually started talking to me again. We became friends with benefits even though it was much more then just that. Over the next few months we got so attached to each other and had a deep love. This wasn't going to last forever and a few weeks ago she wanted it to stop, she was starting to lose feelings for me but things kind of went back to were they were. about a week ago she started acting differently, their was talking to another boy. The past few months I've been trying to get myself to ask her to get back with me, I realized how happy she makes me and how she brought me out of my depression. I asked her last Friday but it was to late, she didn't really have feelings for me. She even tried cutting me off for good on Thursday but I was able to get her to still somewhat talk to me. Ever since then I've just been a wreck. I love her so much and she's lost feelings for me and is talking to another boy. This is the worst pain I've had in my life. I can't relax anymore, my mind is thinking about this 24/7. This morning I learned they did sexual things together last night and I'm just broke. She's all I ever had and she doesn't care about me anymore and has another boy. She was the best thing that ever happened to me and I messed it all up. I'm back in depression and I feel like I'll never find a girl again, it took someone who had a goal to take me out of my shell for this to actually happen. Any advice?