I habe a child support court order to pay $384 per week for three children in Massachusetts. the mother worked per diem bringing hime $70 per week.

In order to get a modification of child support, you most prove the occurrence of a substantial change of circumstance.  Before filing the motion to modify, you should run the child support guidelines using your current income and her ex's estimated income (if she won't share her actual income) and check to see if there is a substantial difference with the current child support order.