Here is some advice that I am not ashamed to dispense here, not as a medical professional but someone who had long covid symptoms for a period of months and spe

Here is some advice that I am not ashamed to dispense here, not as a medical professional but someone who had long covid symptoms for a period of months and spent a lot of time with long covid specialists and doing research (dispensing with the formalities): If you haven't, go to a cardiologist and have them do a Stress Test (they hook you up and watch you for 10m as you walk uphill on a treadmill and increase intensity), and do a test for POTS. One POTS symptom would be dizziness, a big blood pressure change and bpm change when going from a lying down position to standing upright. It's something to rule out. Another something you mentioned suggested exercise intolerance. One way to deal with that is very very slow and steady training of your cardio system and even strength training as well. Going too hard can set you back, but going at the right pace can make you better. [edit]: Some additional information. You pick what you train (running, cycling, some sport, weight lifting, whatever), you do it at the smallest level, and you wait 48-72 hrs to see if you get worse. If you don't get worse, you do it again at slightly more than that pace. If you get worse (I had shortness of breath, insomnia, night sweats, and random chest pounding, but others get debilitating fatigue or other inflammatory symptoms), you back off because it was too much. Another possibility is anxiety (feeling your heart pumping and almost passing out could be physiologically induced, it could be anxiety-induced, or it could be a feedback cycle between them!). All the above I learned at a long covid hospital which had specialists (pulmonology, cardiology, etc.) that were up to date on academic medicine. They were pretty dark, some of them, and as they say a man with a hammer sees only nails. But you sound like you seek answers, and hopefully the above gives some bread crumbs of some use.