I feel awful about a relationship I had as a teenager
What was wrong with the relationship you had?
One of the worst things that ever happened to me. She lied to me that she loved me, she ruined my self-esteem, and she played malicious mind games.
Teens make poor choices all the time. It's part of growing up. Learn from it and move on.
I feel like I don't know who I am. Some of the choices I made in the past have effected me in a positive way, and some of the choices I made in the past have effected me in a negative way.
I'm sorry you have been feeling this way. You should try not to dwell on past mistakes. It is normal for teenagers to make poor choices but that is how we grow and learn from them.