My x wife wants the copays for medical bills for the last 4 years and never asked before now I pay child support weekly.Is she intitled to bring this up now and get it ?I'm in New York

Mostly that depends on how your custody agreement is written. But in general terms You would normally pay 1/2 medical expenses. The flip side to that is she should also be informing you and in some states there is a reasonable time limit that she can ask for them. Not to just simply let them pile up and drop a bombshell on you. You need to check with your state and also your paperwork to see if any time limit applies.