Car Loan Creditors for Ex

My ex and I are cosigners on a van he uses for his business. He has roughly four or five insurance companies he works for, and a local newspaper as an independent contractor. He has ample income. I have not job whatsoever; and am still waiting for a settlement on my workers comp matter. I got a call from the creditor stating that the payment was 20 days late; and that I need to pay because they can't contact him. I told them my story; and the fact that he hid all monetary assets at the onset of the divorce. They kept telling me that my credit score will be affected if I don't pay this. Then the creditor began to "snicker" and said "oh, I'm not laughing at you." Up until now, the creditors never had my email address; nor my current phone number. Obviously my ex must have given this information to them; with possible intents to have them work with me instead. My son and I have just a year and a half to find a job and place to live; while my ex has all of these things and more! Please help with any advice.