Most Helpful Guy
How did you discover he was talking to her? Did you see what the interaction was?
You should be guarded. Odds are pretty good something is going on, but there is a chance they are just talking.
I would suggest just asking him flat out if they are talking. See if he admits they are. If he lies, then tell him you know they are and at that point just hold him to his support role as the father, but not your significant other.
If he admits it, tell him since what happened before, you need him to cease contact with her if you two are going to move forward.
Not that it is OK what he is doing, but he broke it off with you, so at least he isn't running around behind your back.
The key here is open honest communication. At least he is helping you. While it isn't in the way you want and totally need right now, he hasn't ditched you completely.
He clearly has issues with committing to one woman, so be very Leary of him and his intentions. You and your child may be better off in the long run without you two being a couple.
It is sad he has chosen to do this, especially now, but at least you know.
Most Helpful Girl
I'm expecting a baby girl in October, and I'm also having issues with the father. He basically just left me and didn't really give me a reason. And it happened so suddenly. We were fine for the 2 years we were together, up until the last month. Luckily, we didn't live together, so I can't imagine the pain of being kicked out. But I've realized that I can't put up with his bullshit anymore and my baby comes first, he's detached himself from reality and wouldn't accept any help from me. So, as of 5 days ago, I cut off all contact with him, unless it's regarding the baby. It's been pretty easy, because he hasn't even attempted to get in contact with me.
If I were you, I'd tell him that you know about him talking to her, and that you're done with his "bullshit games", and that you deserve better. Tell him you won't contact him again unless it has to do with your little one, and then... do just that. I imagine you love him, so it'll be really hard, but it'll be worth it in the end when he's still immaturely messing around with this girl, while you're being treated like a queen from a guy who actually deserves you. Not to mention, being a single mom will be so rewarding, because you don't have to "share" your little boy.
Anyway, that's what I would do, and that's pretty much what I did do. We can't just wait around for them to grow up anymore. I hope things work out for you, and congrats!