i am really sorry for you.. i just don't understand why to make 4 kids with such jerks like your current and seems to be your previous husbands?
but anyway, MJ's advice is most sensible.. go talk to the lawyer. I am sure, should be some "public" lawyer or so for poor people.. not everyone can afford paying a fortune, but everyone have to have equal rights to defend themselves..look for the "governement lawyer" or something like that.. File the divorce and forcibly make him paying his part for his son.