Missed period - not pregnant

I am 34 (have 2 children both c sections) and for the first time in my life just missed a period. I am 8 days late. I spotted brown for one day. I have taken 4 pregnancy tests at different times of the day and different brands. All negative. I had covid two months ago but had normal cycles even after that. Stress level is insane but no different than usual. No other big changes. I had some joint pain and abdominal cramping in January which lasted about a week and went away. I have an appt with my Dr but it’s not for two more weeks. I am panicking because I DO want more children. Google is panicking me. Has this happened to anyone?