Oh gosh, I am REALLY sorry to hear this. What is so hurtful is that YOU were the stable part of his life. You are the mother of his child. You were not his using buddy that needs to be cut off. Lots of people go through rehab and get clean while maintaining relationships with loved ones that are/have always been sober. So, I don't see this as a normal response. You have expectations of him and he doesn't like it.
I do have a question though . . . are you sure you weren't turning a blind eye to his using while together? There is something called codependency and it is real and that can be why a couple has issues once one gets sober too. Because if someone is easier to appease and deal with when high, you kind of let them be high rather than making waves. It would be hard for me to be in a serious relationship and not be fully aware of someone's addiction problem as you say you were. Were you more aware on some level than you are saying here? Because this is a problem that could haunt you now and for the rest of your life in future relationships. This is something to see a therapist about so that you learn to act on instincts that something is wrong if indeed you were 'unaware' as SOMETHING had to be WAY off if he was addicted to narcotics or if you were codependent in some way definitely explore this. See a licensed therapist and consider Al Anon, a group for those who love an addict.
Now, I find it very difficult to stomach that he has walked out on his child. I DO think that overcoming addiction is very hard and intense and has to be the focus. And perhaps because of guilt or something like that, you were triggering his wanting to use. BUT this is part of overcoming addiction. Learning to deal with the emotions of dealing with people or whatever the triggers are for you. If he does not learn to do that, he will always be an addict and there is always a threat he'll use. YOU can't control that, he does. I will say too that most rehab programs have family programs because it is essential that all learn to navigate the addiction issues. For example, if you are a trigger to him--- your style of reacting to his not doing X,Y and Z triggers him to want to use---- that is a point of communication for you. That you can tweak how you express yourself or what you want and how he can respond without continuing the old pattern. Family addiction counseling helps with these things.
Agree that he DOES have a child that he is responsible for. And your baby deserves financial help. That is his duty to provide.
I'm very sorry about this situation though. Those who are addicts and in early stages of recovery can be erratic. See a therapist yourself hon to help you through this. peace and hugs
Nothing wrong with you that a vigorous child-support lawyer can't help solve. Go see one on Monday.
If he wants to be a dead beat let him make sure u get child support but u don't need someone like that around u or ur baby