Ex-hub

When I was married my wife had very bad credit and could not take a student loan out for her son. I took out a 12,000 dollar loan for him. I payed the interest on this loan for two years but then became permanently disabled. Because of her drug habit we separated then divorced. During the separation I told her I was not going to make the payment on her sons loan because he never went to school. My stepson spent the year up north at his girlfriends house bought him a full meal plan and sent money and extra food and supply's monthly and he finished the year with a 0.58 gpa. During our separation she did not make one payment because the loan was in my name. Because I make a lot more money than her even though I am retired and on disability the court made me pay her 1,000 a month for life and keep the loan. I am happily remarried but went from makeing almost 10,000 a month to 4,200 a month and paying her a 1,000 a month money is tight. Is there anything I can do about this loan? It is at 18,000 now and I can't afford to pay that back. Thanks for any help