Most people that get divorced make this mistake. Lenders do not care what your divorce decree says, unless your ex-husband refinanced the vehicle in his name only (like your lawyer should have made a condition of the divorce) you are still responsible for the loan if your ex defaults.
And if he files for bankruptcy, they will come after you for it.
As a finance manager for a car dealer I see this so many times every month it makes me sick. But, it's the law.
Depending on how much is owed on the vehicle verse what it's worth, you might want to approach the lender and see if you can make a deal where they rewrite the loan in your name only. You would have to get the vehicle from your ex-husband, but at least it would stop your credit being trashed.
Finance Manager for over 7-years.