I find it hard to believe that you had COVID-19 if for no other reason that its highly contagious nature makes it all but inconceivable that you wouldn't have infected others from where it would have rapidly spread.
Also there is no recorded evidence of it anywhere outside of China before late January so with it's 7-14 day incubation period it doesn't fit chronologically either.
Normal Winter flu's are still about so think it far more likely that it was one of those which laid you low, just because you don't normally catch these things doesn't mean you can't!