The best thing you can do at this point, is accept the break up and the fact that he really doesn’t want to date you. It’s great that you can acknowledge that you chased him too much — and that you want to take steps to improve things. To reverse that behavior you simply have to not chase him at all. If he’s interested in the future, he’ll approach you.
I know that you’re upset about the breakup and you want him back, but the best thing you can do is to move on and change the behavior you have that repels instead of attracts. When you do, you’ll be evolving, improving yourself as a potential girlfriend, and you’ll stop wasting energy in your own life.
I hope that helps. 😀