Go back to court and seek an Order stopping Child Support
My name is Stephen R. Cohen and I have practiced over 38 years and can be reached at 213-819-1171. I practiced mainly in Los Angeles and Orange County, California. I am not seeking clients from existing relationships with other attorneys, and give only limited advise over the phone (the phone is primarily used to set appointments), these services do not create an attorney client relationship. I apologize for mispelling< as I am a lousy typist, My answers may offend as I do not believe in pulling punches or sugar coating the truth. Further regarding courts in other states my opinions are largely based on logic and what I think is the modern trend which is to consider the needs of the child.
You can try and get the child support changed, but you need to consider how much more support you have to pay in any event. Unless your particular decree has something special in it, child support typically terminates at age 21. Depending on how many months there are until the child turns 21 and what your payment is, it may be cheaper to just finish paying it than it would be to pay legal fees to get it changed. Consult with an attorney to find out your options and discuss the cost, risks and benefits of each option. The small cost of a consult could be worth your peace of mind.