Well there are two things that you can do here depending on what you want.   First, you can bring a proceeding to enforce the judgement (and for contempt) to force him to pay and ask for a judgement for the money you paid that was his obligation.  Or you can bring a motion for the money you paid (and a judgement if he can not pay) and to modify the judgement of divorce as to the second mortgage obligation but you must be able to receive something in return.  In order to figure that out one would need to read your agreement.  See what the bottom line is for you. I would bring it to an attorney to review. Good luck.