If my ex forecloses on the house, how do I protect my credit?

The divorce action affected the rights between you and your ex. It did not affect the rights of any creditor. Therefore, unless the creditor is willing to release you, you are still responsible for the mortgage. If a claim is made against you, you would have a claim against your ex. This does not help your credit report but you would be entitled to place an explanation on your credit report.

If your name was not on the original loan, or if it was removed as part of the quit claim deed agreement, then it should not impact your credit. However, the lender would have had to agree to remove you from the loan obligation, which is not often done.

The divorce judgment is only between you and your ex, it has no power or authority over the mortgage company. Even though the judgment might state that your ex is responsible to pay the mortgage, if he doesn't, and you are a co-signer to the mortgage, the mortgage company has the right to come after you for the payment. They can spoil your credit rating for his failure to pay and they can ultimately sue you for the entire amount owing. Your only option is to file a motion against your ex in the divorce court to enforce the judgment.

Only protection was to make sure your ex refinance and get your name off of the mortgage.

Your action is in the divorce court, you are still liable to the mortgage company. Such liability to you will generally not be dischargeable in bankruptcy but the foreclosure will be on your credit rating and you can be sued and forced to pay the mortgage company. See an attorney.