hey suzieq!
I agree with GL the best thing you can do is keep on getting healthier and stronger and be an example for your son. Also that its important he knows he can count on you at the end of the day...
Its too bad if he is let down by his father again. But remember its not under your control. You cannot control what he says or what your son believes or not. Hand your son to God/HP...
Man, easier said than done huh... stay strong.