I am 18 years old and I was going out with this girl, she was very attached, and I asked for a break. I went through the break and talked to another girl, this made her very upset. She cried a lot and I didn't act right, I came back to her and we just weren't the same. We had our good and bad days, but now the tables have turned and she wants me out of her life, but I care a lot about her and I really don't know what to do.. I need help

Give her the space she asks for. If you give her enough time she might miss you or she might not come back but you'll at least know for sure. If you continue hanging on then you've already lost, because she will see that as weak.