I am truly sorry you are going through this especially right now, but you HAVE to let him go. You are holding on to someone that you think is going to change. I can tell you honestly, he is not going to and if he can do this to you now, he is incapable of being the guy you need him to be. Of course everyone is going to tell you to forget this loser, which I am sure you would like nothing more than that. It is hard to let go of him because he is the father of your child and you want a family. So I totally get where you are coming from, but you need to focus on yourself and your baby right now and try to put him on the backburner for now.
The first thing I would do is NOT contact him in any way or form, especially by texting. When you engage him this way, he feels even more justified in being a jerk to you. This is how they live with themselfs after screwing someone over. The more you send nasty texts, the more it will hurt you because he will retaliate back. As hard as it is, you need to let him go because he is not the man for you. Just because you have a child together does not mean you were meant to be together. This was something that took me a year to accept myself, so I know how much it hurts and how hard it is. Here is a little backround
I have a 19month old from a man whom I loved, but didnt' love me. He tried to be there during my pregnancy, which he was so I though he cared and we could make it work. When my LO was 7months old (last nov) he left me for another woman that he feel inlove with. Talk about a slap in the face, I was so hurt and upset and humilated. Here I was the woman he was with for almost 3yrs waiting for him to tell me he loved me. He turns around and falls in love with a woman going through a divorce with 3 kids of her own. I am still fighting with not causing drama with him and get to deal with knowing they play house with me son when his dad has him. It still hurts to a point, but my love has faded big time this past year and she can have his sorry ass. It just takes time.
Right now you want him back because you are scared and hurt, but seriously think of what this man has done to you. Look past what you wanted him to be and really look at the type of man he is. I had to do this with my EX and got a whole new side of him after he left. He got nasty, hurtful and unreliable, so I see now this man I feel in love with was a fake and not someone I like.
I deal with the EX now only to discuss our son and keep the conversation limited. It works well for me and keeps me from fighting with him. Take time to mourn your loss with him and try tomove on. Once your baby is here, you will be able to focus on something else and in time you will be thankful this guy left. Take care