What a jerk to leave at a time like this. I would be oh so angry with him. From what you say, I would think mid-life crisis brought on by too much stress: having new baby etc. However, if he is hanging out with a 18 girl and acting single. I would have to think twice about if I wanted him back. You might ask him to go to counseling with you and see how that goes, but I think right now he is just not ready for the responsibility of a new baby, so he got scared and ran. My heart goes out to you. I hope you have a family or friends suppot system, because I think you may need them. Best wishes on your new baby.