If you'd just broken up once, I'd think there was the possibility that it was just a learning experience. But she's broken up with you twice now. It's either the end of the relationship, or the start of a yo-yo relationship. Unfortunately, if it's the second, those don't really work. You go through a long period of going back and forth where your heart gets broken over and over again. Then, over time it completely destroys the relationship. People who can't stay together with each other just don't work out. At this point, even she wants you back, you are really much better off just ending the entire thing. Staying friends with an ex you felt this strongly about doesn't really work either. The feelings are always there, so you end up back together and on the yo-yo I described. I know the last thing you probably want to hear is that you should cut off all contact, but it would really be best for everyone involved.
It's rare to see couples who get together when they are in high school make it, even though so many of them think they well. It's just an age when you are learning a lot about yourself, life, and relationships. Kids that age haven't had the time that older people have had to really reflect on what they hope to find in a life partner. High school kids usually fall in love first and build their dreams around their partner. Then when the feelings start to fade, they wonder why they chose that particular person and if it was really the right choice. This is what I believe your ex is going through. She still needs to learn more about herself and isn't ready for a serious relationship.
You need to focus on moving on and getting better again. Leave things in the past. You will always hold special memories of each other somewhere in your hearts, but you need to move on with your lives.
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy