You could take him to court and ask that he be held in contempt for failure to comply with the court's order as to the house, but it would be a hollow victory, I suspect. If he can't afford to pay the mortgage, he's not going to have the money to pay you to pay the mortgage, most likely.
This is why people need to specify a short deadline for refinance -- or better yet just outright sell the home at the time of the divorce. Your situation happens again and again in cases where that situation isn't handled properly.
I know nothing about your financial circumstances, but if there isn't much equity in the house, which means the bank will come after you and him after foreclosure for any money still owed, you might want to investigate a bankruptcy, which would relieve you of this debt.
There is a bankruptcy question board on this Website.
I'm not saying for sure whether you want to do that, but it's certainly something to take a look at.
