My ex-husband is filing for bankruptcy. Am i responsible for paying a debt that we had when we were both married if the divorce decree says he is

As regards the creditor, it was not a party to your divorce, so whatever the family law judge ordered does not bind the creditor.  On the other hand, your ex-husband's bankruptcy does not relieve him from paying the bill.  The creditor cannot make him pay it, due to his being discharged from his obligation to the creditor, but you certainly can, as his obligation under the divorce was not discharged.  You may want to see a lawyer to get help with this.  Perhaps you want to find a lawyer that does both family law and bankruptcy.