Strange indeed. If you are paying support, your ex is probably listed as the custodial parent. Why don’t you petition to be the custodial parent and get your child to tell the judge he wants to live with you. Then your ex could pay you support.
Are you sure the support isn’t for college? Some judges have been known to try and guarantee that the non-custodial parent contribute to the college fund by ordering support past the child’s 18th birthday.