my ex and i have a son and my ex/his father does not want anything to do with
our son or pay child support for him. I was wondering what I could or should
do about this?

has paternity been established?
are ther any court orders regarding custody/support/visitation?
ideally what do you want to do?

I'm assuming there is a support order in effect. As long as dad pays his support, you can't make him be a part of your son's life. Does dad realize that he is hurting his child by not being in his life? How old is your son?