I think what @doctorhamster may be trying to say is that we don’t know the neurological effects of COVID yet. I’ve been concerned for a while, since I’ve seen the articles that even people with mild or asymptomatic cases are having neurological effects. It could be that it’s causing a hormone imbalance for you, or something in your brain that can’t be read by CT yet (something in the pituitary gland, maybe) that’s causing a lot of overlapping symptoms with anxiety.
If it is something like the pituitary, the only thing you really can do is treat the “anxiety” symptoms (i.e. you don’t have anxiety, but a problem with COVID-affected chemistry is causing the same symptoms, like diarrhea, racing heartbeat, nausea, feelings of anxiety, etc). The sneezing to me is another sign that this is neurological; we have a “sneezing center” of nerves in our brain stem, so if you’re having some kind of neurological inflammation from long COVID it could affect that, too.
Here are my three ideas. 1. You could try treating the “symptoms,” a lot of which line up with anxiety, since we know COVID attacks us neurologically, and wait for it to go away or for us to know more. I know that’s difficult to say, and even more difficult to deal with, but that’s often what people have to do when part of their brain is affected (for example, often people experience anxiety from taking steroids - they still have to treat the anxiety, though). 2. You see a neurologist. Even if your CTs are clear, it seems most likely that your problems are coming from this level and medications that affect the way your nerves work may help (something like gabapentin or duloxetine, as perhaps COVID inflammation has affected your nerve fibers, etc.) 3. Instead of just trying specific vitamins, you speak to maybe a registered dietician about a low inflammation diet (if that’s not possible, try Google or Facebook groups) and see if attempting to lower inflammation makes a difference. Maybe it won’t at all, but it might be worth an attempt.
It sounds as though you’ve been blessed with fairly good health in your life and, as a result, this is particularly hard for you. This isn’t meant to sound cruel, but when you said you couldn’t take anymore, I thought you were going to say you were one of the people who can’t walk around their own house without experiencing lung pain and being short of breath six months later, who aren’t able to work or live or even go out, so I was a bit surprised when you mentioned the transient nature of your symptoms. BUT I also understand that what you’re experiencing is extremely difficult for you, and I know the frustration of ill health, how it can truly sap your hope, so I really do hope you either find a solution OR that it starts improving soon.