Good afternoon, Mona:
This should have been resolved in your divorce decree. If it was not, you ought to go back to your divorce attorney for advice.
If you are on the loan, both you and your ex are responsible for making payments. If any payment is missed, both of your credit scores could be impacted. The longer you wait to resolve this issue, the more risk you have that something related to this house will affect your ability to purchase another home. You should resolve it sooner than later.
What you do depends on whether there is any equity in the house. If you owe more than the house is worth, you could do a short sale. If there is equity in the house and he wants to keep the house and you and your ex can agree on an amount (e.g. hire an appraiser and reduce the appraised value by all debt and cost of improvements made while you owned it), your attorney would probably tell you that with your permission, he could take you off title and take you off the mortgage if the bank approves, or refinance and and pay you your share of the equity. If he has no money to pay you your share or if he cannot qualify to refinance on his own or if your ex is uncooperative, there are ways for you to force a sale (e.g. a partition sale).
Again, it will be better for you to deal with this sooner than later. Talk to your divorce attorney or get a good real estate attorney in the state where your property is located. If you appreciate an answer, please give "thumbs up". For the most helpful answer, please say thanks with a "best answer" click.