Disabled dad needs help

Hello everyone, I’m new here… Does anyone know how I might petition the court in New Mexico, (I live in Georgia), to set aside an original decree, based on the fact that I had no representation during the divorce? Barring that, how about some advice on how to get child enforcement to recognize that the original order intended that the c/s be discontinued when each child reached 18. I have two children, one is 20, the other is 17. I am STILL paying $600/mo for the oldest child and $600/mo for the youngest. I foolishly agreed to this in 1992, …