Will my ex come back?

I wouldn't hold your breath waiting on him to come back. I dated a guy who claimed to be stressed out about school and that's why we weren't together. You have to think about it this way: imagine all of the things you two would go through together if the relationship lasted. He should want you to be there for the good and the bad. Unless you're the reason he's stressed, breaking up with you is not the answer. The same guy I dated was never in a good mood either and this was bothersome. He was most likely planning to break up and needed an excuse. That was it. What would he do if he lost his job or had pre-wedding jitters? Break up with you then, too? His stress is not an excuse for a break up if you meant that much to him. It doesn't seem like you are over him if you are thinking about a comeback. Let him go because he's moving forward quickly, with or without you. Don't kid yourself. You have a life to live.