medical that is owed by ex for Children and does who claimed child on taxes matter?

Hi, I live In Massachusetts I have 2 children and my oldest who is in college has come been diagonosed with diabetes this past july. My ex has not paid his half of the medicals that has incurred from either child which consists of copays for prescriptions dr's visits and dental visits. I was wondering if it would be to my best interst to bring him in for contempt of the court order that was made when we were divorced. It isn't quite this simple either. My ex is suppose to be able to claim my oldest for taxes well he hasn't since 98 taxes because first he had one year that my son was not in school before he went to college and then the next year my son had asked if he could claim himself because work had goofes on his pay check all year having him claiming 2 which would make him have to pay taxes. My son's income is low he is only employed part time and pats for his own school books. well after my ex said he wouldn't claim him and allow him to claim himself which this was only a verbal agreement, My parent plus loan was denied and we found this out when the semester was almost over and ocer 2,800 was owed and if it was not paid he would not get credit for the courses that he was in now and almost done. I had told my son that if I claimed him I could get earned income and would be able to pay his tution that was due and also pay what he would have to pay for his federal taxes. Which I did and I paid those off and after the payment I had less left if I didn't claim him and didn't pay his taxes. So I did not make out on this deal it was just to help our son with his schooling. I didn't mention it to my ex because anything due with money he blows up and gets quite angry with me. I tried after 9 years to have my child support increased and he was quite angry and verbal about it and it ended up that he was only making 2,000 a year more than I so I didn't get anything more but if he had showed me instead of screaming at me I never would of taken him to court I am not out to get him but I do need to survive and raise these children. The issue of my son being out of school for one year between high school and college wasn't an issue and still receives medical insurance for him and child support. When he has paid me his medical that was due befor it was always $10 a week at a time. I just wnat to know what I can due and if thetaxes willl effect it Please email me at [email protected]. Thanks Deb