You sound like a very responsible, mature young woman. Give yourself a break and concider yourself lucky that you learned this lesson so early in life. Many people do not learn to be themselves until much later in life. You cannot change the things you've done in the past the only healthy productive thing is learning from your mistakes and do your best not to repeat them. I am not trying to make light of your feelings, but I don't think there is a person alive that doesn't regret things they've done.

On a side note you're not alone. The terrible two's are famous for being the most difficult time in a child's life, I disagree. I think it's somewhere in the 11 - 13 age. Each one of my kids went through a period of not being themselves. They went from respectful well-mannered children to the complete opposite. It was difficult to deal with from my point of view but it was no picnic for them either. Think about all of the changes going on in your body, new hormones out of whack and you have no clue how to deal with them. Once things leveled out they returned to themselves.