Am I a jerk for wanting my ex back after I dumped her?

No, It's normal to miss a person we had feelings for and loved and spent a lot of time with...however, you should not ask for her to come back. If she treated you badly, you had a good reason to break up with her. Break ups are painful and they hurt, but this is normal and it will pass with time. It seemed like you did all you could to make the situation work, and it didn't. If you were to ask her for another chance now, things will be worse this go around. You just need to work through the pain.