Most Helpful Girl
He sounds like trouble. No, you weren't together, but since you two kind of had a thing, I think he should have told you directly that he was going to be in a relationship with this other girl. You deserved an explanation from him and not some public status update on Facebook. Also, the fact that he texts you that he misses you while he's still with her is a huge red flag. He should resolve the problems he's going through with his girlfriend and not go behind her back and talk to you. It's a sign of unfaithfulness, and if he has no problem going behind her back, he'll have no problem going behind yours either. And lastly, it's very unhealthy to jump from relationship to relationship. Even if he did break up with her now, you would still have to wait a while before being with him. Otherwise he would just take the baggage from his previous relationship and move it to your relationship, which would not be good nor healthy.
So to me he just doesn't sound like he's worth it. You deserve someone who will want you the most, and not just sexually. Because it does sound to me that since he's gotten everything from you (sex and so on) without committing to you, he probably doesn't want to commit in the future. Sorry. He wants to have his cake and eat it too. And as I said, he sounds like a cheater. So to save yourself from more hurt, just move on.