Well, sweetheart, medical anxiety is a real thing. MedHelp hears often from people who have it, especially in some of the communities where there is a combination of guilt over one's behavior and a condition that is undesirable, such as, the STD community. If a person can find a way to castigate themself that they could have unwisely brought an illness or condition on themself, they can go into a downward spiral of obsessive worry.
One of the few good things about the pandemic is that people are more readily able to make online (Zoom call) appointments with therapists and counselors. Do you have access to any such resources? For example, if you are a student, do you have a counselor associated with your school with whom you can talk?
If not, I do hope you realize that the number of people who die from Covid is pretty small, compared to the number of people who get sick from Covid. Except in places where the health-care system has entirely failed, the standard of care and the understanding of how to treat the illness has improved greatly since the beginning of the pandemic. And the understanding of how much good it does to mask, wash hands, and social distance has improved greatly as well. They are opening schools because they have found that social distancing and masking have kept the virus from spreading in the classroom, for example.
This is a difficult time, and there is nothing wrong with needing some help from a counselor. Possibly someone will write in with resources for online groups, but do avoid any where people are simply sharing their fears and egging each other on. Treat the situation with as much logic as you can muster. And read up on medical anxiety, it can help.
If you have symptoms of covid, and you do, you need to get tested. Period. There is no other way to know if you have it or not, as most people who get it have mild symptoms or no symptoms at all but they can still pass it on to others. The only reliable test is a PCR test, and you should be able to get one pretty easily at this point in the epidemic if you live in the US and especially if you're in a populated area. In the meantime, the advice is to quarantine yourself for 14 days or until you get a couple of negative PCR tests back. I know you want to avoid this. I'm a huge anxiety sufferer, and I know avoidance. But it doesn't help. So first you need to deal with the possibility you have covid, as you might. It's a pandemic. You don't have severe symptoms and at this time of year it could well be seasonal allergies. But again, the only way to know is to get tested, and if you don't want to do that, you have to isolate until all symptoms are gone and then another several days after that. The exact advice can be found on the CDC website. It's also important if you do have covid to find out early, because if you are in fact a high risk person, and I'm not sure sinusitis makes you one, that isn't even a disease, it's a symptom of some diseases and also of allergies, there are actually treatments that can pretty much cure you if you take them early enough. They can only be gotten through a doctor or hospital that knows about them and has facilities for you to take them, but they do exist. If you were paying attention, it's very possible former President Trump's life was saved by one of these drugs. As for the anxiety problem, after you do whatever you need to do to rule out covid, do get therapy for your anxiety. And get vaccinated as soon as possible. Peace.