[stonescar]

Fishsticks
Although I'm just 22 years old, I'm in a relationship now for 4 and 1/2 years, living together for the last 2 years. Before we got together I experienced almost the same thing with my ex, we'd been together for a couple of years and she had left me, but came back just at the time I stopped giving her attention. I know we were young at the time, and you probably still think I'm young, but in my experience some girls often react this way.

I obviously don't know what your ex' reasoning behind this is, but there some things you should consider. She might just be missing your nearness and companionship, like fat nicky said, and come back for comfort. In a different perspective she might also really love you, and that's why she can't leave you - her attemps to break up might be a way to avoid a confrontation, kind of a cowardly way out, if you have problems to talk about. It might be in frustration, to be heard, to tell you something is wrong.

I know you're sceptical because this has happened before, and you don't wan't to go through this again, but if you really love her, I think you have to talk with her. Tell her what you have told us. Let her know that a part of you wants her back, but that you don't want to live in an insecure relationship. Talk to her about the future, find out what you both want. If she loves you and understands, you'll work it out.

These situations can really hurt, but it can also be a turning point in a relationship, if you both want it. Maybe this will lead you closer together, and help you get past the problems you had before. After 4 years I had problems in my relationship as well, because we started to take eachother for granted and lost the good communication we had. Living together can be hard, and sometimes you forget to appreciate it, until it's gone.

I'll stop babbling now, tl;dr and all that.
Bottom line: talk to her, don't give in to the feelings that want her back until you're both sure you want to work things out between you.

EDIT:
And, like the others have said. If you both want this it will survive having some time apart, to gather your thoughts and feelings.