i m sorry that you are hurt, and i understand how you feel.
when you got together with your b/f, he got out of a relationship with his wife, usually guys want sex and not jump back into another relationship with another person. it is possible that he just needed some space away from his wife for awhile.
and being with a guy who has kids, you have to know that they will always have contact with each other.
i m a single mother, and my son's father dumped me 13 years ago.
you have to eat, you have to take care of yourself, for your baby. you probably cant see it right now, but everything is going to be okay, even if your ex isnt in your life. you can make it, and you will be fine.
forget about him and concentrate on that baby.