Had a severe case of COVID in March 2020

got PCR tested like 30 times, every single one came back negative
got antibody tested 30 times, negative every time
even purchased a T cell test, also came back negative. All tests were during the year 2020, so it's NOT due to fading immunity

and yet that illness in March was the worst illness of my life, and I thought I was going to die
my symptoms were mostly tachycardia, gastrointestinal and fatigue
I had severe O2 drops but they were short-lived, lasting only a minute. No lung damage.
The first episode of tachycardia had my BPM over 300

I also suffered long-COVID, and I saw many young people in New York doing the "covid walk" (where you take forever to take 2 steps forward because you're fatigued). I even asked one young woman and she told me she was sick from covid.

So why are COVID patients testing negative for COVID? And if my symptoms aren't from COVID, why did they so suddenly strike RIGHT at the date of March 2020, and why did I see dozens of other people with my same symptoms? Please high IQ responses only