I am so sorry to hear this. Your experience is actually very similar to mine. I was bullied very badly when I was young (in elementary and middle school) and I ended up not having friends or wanting to go anywhere when I was in high school either. A few years later, my life is still affected by my experiences too. I still always worry people won't like me, I am scared to talk to people sometimes because I am afraid they will say something unkind, etc. I do not know why people can be so mean. I think younger people do that to get attention, but it is so wrong.
I know how easy it can be to feel resentful toward others because they've treated you unkindly, and to feel angry because of it. However, how about rather than to feel angry about the situation, turn it into something positive? Of course recognize the fact that it was wrong, but use your experiences to help others. Speak out against bullying, help others who are in that sort of situation, or focus on helping others in any way. Again, I know how easy it is to be resentful, but you can also choose to be a better person than they were. And that is much more worth your time than anger. Don't allow someone else's negativity to hold you back from living a positive life now or in the future.
I hope that you can resolve some of the concerns you are experiencing as a result of the bullying. Perhaps you can try counseling to try to resolve some of the concerns? This may help. It may also be helpful to focus on the strengths you have, or the good things that people have said about you. It can be easy to remember the bad things people have said about us and focus only on those, but remember the positive qualities that others have recognized and the positive things you notice about yourself as well.