From a credit perspective, there will be a significant impact on your credit report if the mortgage held by you and your ex-husband goes into bankruptcy.
The tradeline will be reported on your credit report as being included in a bankruptcy; your credit score will drop and any credit cards held by you could exercise their Universal Default clause and increase your interest rate to the state maximum.
Further, your credit history will appear to have two bankruptcies. Obtaining credit in the future will be very challenging.
The problem lies in a common misunderstanding on divorce decrees regarding joint accounts. Although the divorce decree may require your ex-husband only to pay the joint mortgage debt, it does not overrule the contract between the bank and you with your ex-husband. You are still contractually obligated to pay your ex-husband's mortgage if he does not. The divorce decree gives you grounds to sue your ex-husband for damages for his failure to make the mortgage payments, but it does not give you any protection from the bank. The bank could possibly sue you for the entire mortgage balance if your ex-husband obtains protection under bankruptcy laws.
As the posters below note, you need legal advice qucikly. Contact the attorney who handled your divorce as soon as possible.