I swear I had this shit last year. In July or August of last year, I came down with a bug that felt just like the flu. Sweats, fever, chills, coughing, that kicked my ass for about 7 or 8 days. I mean, laying up on the couch, don't-want-to-get-up-to-go-pee kind of sick. Went to doctor's care and tested negative for the flu. Took some antibiotics and finally got over it. Makes you wonder how long this has actually been around and we just didn't know it, or blew it off as a bug of some sort.
It's common for people to think/hope that they caught a particularly virulent circulating bug (happens every bad flu season), but unfortunately, the modeling simply doesn't support that.
We can see 2 simple indicators:
1) look at how fast and hard this hit the US, once it began. If there had been community spread in the US back in November or December (like some believe, again, citing their, "I had something. It swept through the local community" anecdotes), much less any earlier last year, we would have been well under way in January-February.
This bug is HIGHLY contagious. You might've heard/read of the term R0/R-naught. That's the reproductivity of an infectious pathogen (how many other people, each infected person will in turn, infect). It's back calculated from how quickly, and wide, this spreads. Seasonal flu has an R0 of about 1.2.
The R0 for this bug WITH all the social distancing measures in place is STILL 2-3. The R0 WITHOUT the extreme SD measures has been estimated at around 5-6. It spreads like wildfire unmitigated, and the numbers double every 3 days or so. Back calculating the numbers, the US really only started community transmission about the end of January.
2) while there are issues with false negatives in the tests, the fact remains that ~90% of the people WITH symptoms who've been tested, show negative for Covid-19. There are just a lot of other respiratory illnesses going around as well.