I feel for you and relate to how down you are. I am down too right now, and just joined last night.
I am on a moderate dosage of an anti-depressant, which has been somewhat helpful; therapy I've had to forego for now due to money.
Keep in touch with us, and remember what the others have said: we can't change our past.
And trust me, when I think about my past and all of my regrets, I can get very, very down on myself. But logically I know we cannot go back and fix our past. We can only try to become better people in our present and in our future, and learn from our past.
Be good to yourself, okay?