I think he was telling you the truth, that he regrets his sudden boost into the world of being a grown-up and having obligations, but that does not mean he doesn't love you. He is probably just scared or resentful to have to grow up, to a world that looks like guilt, responsibility and worrry. I don't know if your marriage will survive him feeling that way (it doesn't sound like he's trying very much to pull up his pants and be an adult), but if it helps, women sometimes get that way too, and also have to figure out how to accommodate their fears of loss of freedom and fun. The mistake he made is telling you how he feels in such a rude fashion. If he had said, "Honey, the baby coming makes me feel vulnerable and like I have to put away all the fun of my younger life and just be a boring adult who never gets to go out or do what he wants," you would have been able to commiserate and maybe problem-solve so when the baby comes you two can still have nights out, and so on. But instead he just stuffed it and acted mad, and is now making plans to run away. I see red flags all over the fact that he didn't even tell you.
All you can do is sympathetically ask him if he wants to run away, and see if there are plans the two of you can make where he gets every other Saturday to see his buddies or the two of you go out every other Saturday night, or other things that he thinks he is going to miss. If he won't even go that far with you, go to counseling, together if possible or if not, alone.
I am sorry you are feeling like this. Congrats on the baby. I can not speak for
your husband but maybe he is scared or feeling overwhelmed. IDK? Just thinking that it may be a reason for his behavior. Unfortunately , most men take longer to mature then woman and for the most part in their mind the world revolves around them. Not so much selfishness but being self centered. A lot of times they do not even realize it. Have you told him how you feel?