Aw hon.
It's very difficult to be with someone who doesn't put you first. I don't have any real advice, except that you might think you can't do it alone but you certainly can. However, counselling is the first step, if he'll do it. My DH is a smoker and a weed smoker, and likes his cans, but he doesn't smoke around me because I'm preg FGS! It was a struggle but now he gets that smoking round me = smoking round the baby.
He sometimes gets on my nerves when he buys weed when we are skint, but again we talked about it and he's agreed to stick to £10 a week on a friday and if he runs out, tough. It's all about compromise.....I can easily spend that much on magazines/chocolate/whatever.
I think you have a relationship based on love, yes, shared children, etc, but the start of it was forced by your pregnancy. Maybe you didn't have enough time to set the groundrules? If I had moved in with DH immediately we would have split up by now, I know you can't change a person but you can change their habits if you start from the right angle! We were together for 2 years before moving in together so had a good basis. I know that's not so helpful to you but what I mean is maybe you need to go to counselling to talk about what you both want to be the basis of your relationship - to try to go back a few steps?
I don't know, if you love him it's worth a shot, but if you are only with him because of habit and fear of being a single parent, you need to know you can do it alone, if that's what you have to do...
Good luck, keep us posted xxx