Have you ever been in therapy for your depression? A good psychologist is where I'd start, and he or she can help you decide on a plan to get going again. The more you avoid, the harder it gets to stop avoiding things.
I am so sorry that you are regretting your past. We all do things that we regret but you have to forgive yourself and move on. That was then and now is now. Is there anyone you can talk to about it? The hardest thing is to forgive yourself. If you have upset someone or some people ask them for forgiveness and say you are truly sorry and tell them how much you regret ding whatever you did. If you can't talk to them then go to a church and talk to God - he listens and won't tell! Or write a letter of confession about the things you did and then go and burn it.
Don't let it ruin your life. You have your whole life ahead of you and things will get better. You have friends here. We don't know who or where you are. I hope this helps. Remember you are loved - wrap your arms around yourself and give yourself a big hug and tell yourself that you love and forgive yourself and then gradually you will start to feel a sense of a burden being lifted. You have safe friends here to talk to.