There is a statute of limitations for child support. If you didn't have a judgement for child support then you may be out of luck, but if there is a judgement by the courts, he may be liable still. My best advice would be to consult a lawyer and see if there is not something you can do. I am sending you a link that gives you the statute of limitations by state. Go through it and see if you can't get some help on this.
http://www.child-support-collections.com/statute-of-limitations.html

