Should I take my ex back?

[Maddie]

We broke up in December. It was a lot of pain for us both to bear. Then he started dating this girl he used to make fun of. We didn't end on good terms, at all. Well recently we began talking on twitter where everyone could read them. Even his gf. Then he DM me and told me he still loved me and that he was sorry. Then he gave me his number and we talked. He admitted he cheated on me. He didn't do anything with the girl but flirt with her. I'm not really sure if I consider that cheating. But he does. A couple days ago he asked what I would say if he asked to be my boyfriend again. He also tells me he misses me and loves me. He has a girlfriend though. So that would be kind of cheating too, right? I know I really don't want to be with him cause he does cheat, but not extreme, like sex. I'm just curious. I'm wondering what everyone else thinks.