You need to look at a copy of your divorce decree. Does the divorce decree state that you will pay for half of the marital debt, Does it state that you will be living i the house and paying the marital mortgage debt. Whatever the divorce decree states is the rules you will need to live by.
If you need help interpreting the divorce decree, see an attorney or call your attorney that represented you at the time of the divorce. Do not pay for a home that you are not living in unless you were court ordered i the divorce decree.
Is your divorce finalized? If not included in it that he has to refinance or sell to get your name off the mortgage.
If it is finalized regardless of what the divorce decree states if your name is still on the loan and he defaults it is going to reflect on YOUR credit.
Also if he does refinance you may have $ coming to you if property taxes and insurance were part of mortgage payments.
Contact the mortgage company and let them know you want your half.