The problem I see is that although you likely don't have covid, you have something else that may be catchy. Seasonal flu is going around.
So I think you should stay home over Shabbos and get better.
By Sunday night it should be safe enough for you to go to shul.
But, as PlatinumGuy points out, fasting is the deoreisa. So if you're not yet up to staying in shul the whole time, take a nap and come back for neila.
I'm shocked someone would suggest to be lenient on a question of pikuach nefesh with limited knowledge?
FYI - Even PCR tests have very high false-negative rates, so a "negative" result cannot be confidently relied on in-of-themselves e.g. if you have symptoms (or possibly extensive contact with someone covid positive). That is why you need to consult your frum doctor and/or rov.
Look this up:During the first several days after infection 100% of positives cases will show up as negative on the PCR test
the rate of false negatives then declines (as the virus peaks in strength) to a low of 20% (that means of 100 positives, 20 will still show up as negative)
False positives are much lower.
Speak to a rov and/or your frum doctor.
If you are told to stay home, that is what Hashem wants, similar to it being Ratzon Hashem for Hatzoloh people driving around on Yom Kippur, or mothers home with their young children.
