I would suggest talking to a counselor. It gets better, but you are in the one-day-at-a-time stage right now. Since you have a child to take care of, it's important that you get some mental help.
I know it is an old cliché but time does heal wounds. It really does. You were in love. Your head knows all the reasons he was a crummy partner. (and he really was -- you are so much better off without his uncaring, unhelpful dead beat butt on your couch all the time) but you are letting emotions get in the way. When it comes to love--- I'm not all romantic and dreamy . . . I'm practical. Choosing a lifemate should never just be on emotion of the moment because that can change--- it has to be on the business like things of making a union. Similar work ethic, respect, caring, companionship, attraction, shared values and goals, etc. When you have the more practical sides in the bag for choosing a mate, then relationships last longer.
Anyway, agree that you are a bit in the grief stage and that a counselor may help. You have a young child who REALLY needs you. You're the stable parent in their life and they want you to be fully present and engaged and not wounded over a man that treated you badly.
Keeping a journal can help. Get it ALL out in that journal. Stay busy. Connect with others like family and friends who care about you. Exercise as it is a natural way to relieve stress and depression. And if you can see a therapist, that would be terrific. If you feel you may truly be depressed, talk to your doctor.
It sounds really hard and I'm sorry---- but it should get better with time. It hurts more when you have a child together and unfortunately, it means you always have to interact on some level due to the parenting of a child together. By the way, sure hope he is paying child support! That's his duty!!