Personally I would file for divorce & force him to pay child support...no wonder he doesn't want to get divorced....as long as he isn't legally divorced, he can't be held responsible by the court to pay any support for your child that he's the father for....sounds like his not wanting a divorce is just another way he wants to manipulate his lack of responsibility......
Be wise on your part & file for divorce....if he does really want to come back.....worry about it after you make sure you & your new baby are protected from his irresponsibility. Filing for the divorce & nailing him with child may be a wake up call for him to let him know that he can't escape his responsibility & just run away.....but I would definitely NOT just take him back....definitely in the least he would have to be tested for anything he might have picked up through his irresponsible actions.......& I doubt after this that I would ever be able to trust him ever again IMO.
Best wishes.,....no one should be treated like he's treating you