In fact, I just read your post about him, and it sounds like he is not trying at all. Not even phoning, nothing. What does "trying to make it work" mean to him if he is not doing anything? Maybe he just had in mind that you would not hit him for child support if he pretended that he wanted to be in a relationship because you would be afraid he would get mad and not be there for you. But since he is not there for you anyway, sheez, call a spade a spade and see your child-support attorney.
Interesting problem to have. If you can support yourself (with child support from him, or alone), I don't see why you have to stick with him if you actually don't like him very much. I mean, if there is a general disinterest in ever being his romantic partner again, you'll never make it past the stresses of parenthood. Or if he only wants someone to cook, clean and have sex with (and I hope it goes without saying, if he only is there to sponge off of you) I would definitely consider kicking him to the curb. He's got to be a full contributor and it doesn't sound like he is trying very hard to make things work.
Leave? Talk to him about how you're feeling?