It sounds like your ex makes more money than you do. In our agreement-yet to be finalized but drawn up with both attorneys present-as the custodial parent I pay the first $250 in medical expenses a year for each child. After that he pays the percentage towards the bill that he pays in child support. So he's paying 61%, me 39%. I do carry the health insurance for the kids which is really pretty good. If he is making more than you, could the agreement be amended to reflect your incomes? That isn't a fix for the insurance issue but it would help. Just a thought.