Seek help from an attorney to modify the agreement that you entered in to and see if you need to do any thing with regard to the court order that probably encompassed the agreement as well.  And I would strongly suggest that your ex husband also have an attorney during this process and to make sure that the modification agreement specifically states that you have both been advised of your rights by independent attorneys.  This will protect you in the future from him saying anything to the contrary.  The documents from your divorce need to be read to determine the best guidance to be given here.  And please o not try and do anything on your own.  It can only back fire. Good luck.