I have recieved a notice for a review/modification of child support.

I divorced in 2001, in the original documentation we have joint physical and legal custody, I am required to cover medical insurance. Also I am not court ordered to pay child support. But through the years, I have given money monthly, buy most of the clothing, and per the original I was to claim one child and her the other, but the last two years I have let her claim them to help her monetarily. Now she is trying to amend the original order. I also live in another state now as she had one time moved to Texas with a person she met off the internet. Which state am I covered under? Is it GA because of the original order and that is where the kids are now. Need help to figure out what to do. Thanks