Maybe you didn't have covid in March, maybe you did. Maybe you do have covid now, maybe you don't. You might get it in the future or maybe you now have a bit of immunity.
It's just a shame science hasn't come up with something like a test to confirm if you have or haven't, then you wouldn't have anxiety about if you do or don't have it.
If science did come up with a test and you still refused to use it, then this anxiety would be self inflicted.
If you ever want to escape anxiety you have to make an effort to stop self sabotaging or you will never alleviate your problem.