Checking my last day of health coverage - 18 weeks in

I was told my coverage ends on my last day, but the letter says the end of the month. It has been weighing on me all week. I have an appointment next week. Did coverage match what HR said?

Dental and vision sometimes end on a different date from medical. Mine did.

Ask HR to confirm the exact date in writing. I also called the insurance company to double-check.