I missed my period but the tests were negative

K

I took two tests and both were negative, but I missed my period (it’s like 2-3 weeks late). I was on birth control for a couple of months and after stopping it my period stayed the same as when I was on the pill except it came the last Tuesday of the month and when I was on the pill it came the last Wednesday of the month. Last month it came a couple days around the time it usually comes (not the exact same day, it came a few days earlier/later) and now this month I have missed it. Has this happened to anyone else? I have a gynecologist appt this week.