Why doesn't anybody want to be my friend?

People always seem so mean and cruel. No one ever tries to help me with anything. All the friends I've ever met replaced me with my brother and won't hang out with me anymore. I was adopted and am the only black person in this "family". I am trying to go to college but in high school my mom pretty much gave me to CYS services in 12th grade and they put me in placement and the grades from my 12th grade year were all F's because I didn't get to finish so that put me at the bottom part of my class and I was an honors student and I don't think I'll be able to get into college now. On top of that I haven't had any close friends in many years and I feel so alone and lonely. Why are people so mean? What can I do?