You may file a motion to enforce. The court can order him to commence payments to you again, and the court can reduce the amount owed to a judgment. Judgments accrue interest until they are paid in full, so it provides an incentive to your ex-husband to pay it off. Additionally, you may record a judgment and, if he doesn't pay, you may seek a garnishment.
The information provided is general in nature and does not create an attorney-client relationship.