Rapid tests work very well at not signalling false positives, but false negatives happen all the time. The CDC has recommended "serial" testing in order to better establish someone's COVID status (but people aren't exactly given enough tests or money to do that).

If you ever get a positive "but faint" test, you're positive, a positive result is a positive result. It's an alarmingly common misconception people have that the boldness of the line is some signifier of infection intensity, even though tests can't measure that and don't try to. The CDC should have gotten ahead of the natural inclination people have to downplay results that make their lives miserable but :shrug-outta-hecks:

edit: Some people with long COVID can test positive after they stop being contagious

Rapid Antigen Tests have around a 15-20% false negative rate.

There's a significant chance you have Covid.

you're basically supposed to test a few times with like 12 hours between. it sucks because they are expensive and the govt only gave us a few freebies. seems like the kind of thing everyone should get in the mail once a week but we are in a hellstate. there are constant false negatives depending on many factors but the positives are almost 100% accurate. so sensitive you will often still test positive way after you are no longer contagious.

You need to be noticably sick for 2 to 3 days before you can test positive on rapid tests.

Can you do a PCR test?

I think the general recommendation is to take another rapid test 24 hours later if the first one was negative and you feel ill. Theres a decent chance of a false negative, but two in a row is significantly more likely to truly be negative.

I thought I had Covid recently but it turned out to be the flu. It might really be something else.

Nah