I don't fit your Covid category,

but, in the fall of 2019, I was teaching high school. The school nurse and I both observed that there were a few students with really long-lingering coughs. It did not seem to be highly contagious. I have thought since 2
January of 2020 that it began in the Fall of 2019.

I take immune suppressing medications and so try to be alert to infectious situations, especially when I was teaching and exposed to a lot of students. The school nurse was very supportive of my situation.

I really just want to scream!!!! about doctors not listening/not believing. It took 35 years to get a diagnosis for my autoimmune disease. My mother starting taking me to doctors when I was 17...got diagnosed at 52 yrs old.
You really, really have my sympathy!

Good luck!