Monetarily - close any joint accounts so that he does not indebt you further. It's hard if he has you in credit debt - when I left my X I went to the bank and told them the situation, and had to pay off the credit card before I could get my name off of it... he kept the stuff, I paid for it. But at least I don't have bad credit now. Explain what has happened to someone at the bank, and they may be able to help you work out some kind of payment plan with less interest, and maybe even make sure that the boyfriend pays his share. Watch your back with the bank while that guy is taking advantage of you, he might not want to let a good thing go so easily.
Once you have work (Which is understandably hard with a seven-month-old, and while depressed), or at least some kind of money coming in (don't be afraid to ask for help, most people have to at some point in their lives) things will look a lot brighter.
I think talking to a counselor would be really helpful for you at this point, not only to talk about the emotional repercussions of your relationship with this guy, but also to make a plan for your future. You'll feel better when you've got steps laid out for you, it will take a lot of stress off.
Be strong, lady. We're all hoping for the best for you and your little boy. You can do it!