Early on when this started for me, I was more of open mouth breather and I think I did snore a lot. The first time I started the breathing exercise regimen, part of what I learned was to change the open mouth breathing to just breathing through the nose, even during exercise. So for the first three days, I only did nasal breathing unless I absolutely had to breathe through my mouth such as when talking. But even then, each inhale during talking is through the nose. I even taped my mouth shut at night, every night for a good few weeks. But the first three days or so in doing this, that's when my symptoms greatly diminished. So to this day, I nasal breathe and I think this helps to keep the symptoms at bay.

I think that's a good idea to ask for more specific help from your doctors. Physicians are mostly general physicians who have knowledge in various areas, so it's kind of a "helping them to help me" type situation.

I hear you about getting frustrated with all the tests and medications. I felt the same, though over time when I accepted that I would be dealing with this for a long time, that it made me feel better and turned the search for answers into more of a journey than trying to rush to find an answer.

I think a sleep study will be worth it. It may discover something, who knows. But I wonder if your Covid symptoms sort of transitioned to a "long covid" that I've heard about and briefly read upon. So I think there is some hope of the possibility of the symptoms diminishing over time, but just more slowly than others.