How could I get custody of my children?

I need to know how to prove that I was not notified for a custody hearing? I also need to know what I need to do to prove that my caseworker is not doing what is in the best interest of my children. About 3 years ago I divorced my children's father because he abused me and one of my children and then when he got out of jail he accused me of doing the same so for the last 2 years. I have been fighting to get my kids back as all of this has been going on my ex-husband has gotten an open cps case and my children are still placed with him and they are not even thinking about removing them from his care. What do I do to prove that he is the one that is the unfit parent and should not have the kids in his care? Can you please help me?