I'm having trouble breathing fully, like I can't completely expand my lungs or part of them isn't getting enough oxygen. I find myself waiting to yawn to feel like Im finally getting enough air. This happened last year too, and the doctor said it was stress and it went away in two weeks without any meds. This time I saw an MD pulmonary, and they did tests for thyroid, which came back fine. I'm negative for COVID, and all my lipid and liver function tests are okay. But now I'm not sure who to go to next, and the difficulty in breathing just seems to be getting worse. What could this be?