Mixedmedia has given you some great ideas. I second the Buddhist reading. Thacht Nhat Hanh is a great author. When I first started reading him I started with Peace is in Every Step. I made fun of this book with every page turn. But in the end, I appreciated it and it helped me put things in perspective and live a happier life. I used it to get out of my depression, but I'm sure it would help with other things.
Another things, I feel like I'm attacking you, but I feel that maybe that might help and if not tell me to shut up, it won't hurt my feelings any.
I read your life background and it's very similar to mine. Except, I never felt like I was mistake. I was an only child and spent a lot of time alone because both of my parents worked long hours. I dated a guy who mentally abused me by constantly telling me I was lucky to have him because I was so ugly no one else ever would and other crazy things just to keep me. I was never very social and thought very lowly of myself because of these things. But...
You have to get to a point where you dismiss all the people that treated you like shit in the past. You have to realize that you are using them as excuses to feel the way you do. Everyone blames people for their problems...parents are the main targets. However, once you reach a certain point you have to take responsibility for yourself. You made the choices to act the way you are acting.
Everyone does bad things. That was in the past and you are in the present working towards the future. Do you want to continue carrying all that baggage? I left my best friend stranded on a street corner after blowing smoke in her face because she said something about my smoking so I kicked her out of my car. That is just an example of things in my past. Everyone does mean things in their teen years I think, even if it was unintentional. But you need to forgive yourself and forgive others for their stupidity.
Good luck tomorrow back at college. Just remember you have the power to be whoever you want. You made the choice to be hard on youself, you can make the choice not to be. It'll take time...you won't wake up in the morning and be in love with yourself. You've taken the first step by admitting that you are unhappy with the way your life is going. Now you need to take steps to fix it, whether it be taking our 2 cents or seeking counseling through a professional.