Can your ex's health insurance company back-date your coverage termination date to the day of the divorce legally?

My ex tried to take me off his health insurance 1 mo. after we separated,but couldn't b/c we were still married. 2 yrs. later,I paid for the entire divorce & mailed him the final papers. He waited 3 mo. later, then took me off his insurance & didn't tell me. I had some lab work done & ended up getting a $350 bill. I called the insur. co. who told me that my coverage termination was back-dated to the day my divorce was finalized. I assume I will get 3 mo. worth of doctors bills if they're allowed to do this. It seems as if the day he literally produced the divorce papers is the actual day that my coverage should have ended, correct?