There are options available to you. I suggest you contact an attorney as you may find that the expenses of counsel in relation to the amount of financial obligation you are being deprived of will likely justify having the assistance of competent counsel to aggressively pursue that which you are entitled to and not receiving from your ex-husband.
Divorce agreements are usually incorporated into the divorce judgment. This makes the agreement a court order and permits you to file a motion for contempt when enforcement is needed. Contempt motions are decided fairly quickly, within weeks. Attorney's fees may be awarded to you if your former spouse is found in contempt.
Your question may not be a complete or accurate description of the problem. My answer is not legal advice. No client/attorney relationship exists by virtue of this answer. Laws are different from jurisdiction to jurisdiction and frequently change. Do not act on any information provided without consulting with a lawyer licensed to practice in your jurisdiction who has experience with the kind of issues that concern you.