Similar to other commenters, I changed my diet drastically and added supplements (ALCAT plus Leo Gallands long covid histamine elimination diet). I feel much much better (PEM is going away), still have bad brain fog, but have recovered some physical stamina. Surprisingly I have lost weight, look better and have lost puffiness that I would sometimes feel in my face and eyes, that no doctor had an answer for. For me this diet is no grains, dairy, beef, nuts, fruits limited to berries, and tons of greens (cooked) mushrooms onions olive oil, coconut, seeds, water- it is a wild diet that is completely different for me but seems to be working!