I have an autoimmune disease and long covid sounds so much like it! Try these things:
1. Hydration: make sure you get 32 oz of liquid daily and that your pee is light yellow.
2. Eat right. Move toward non-processed, low sugar, high nutrition.
3. Take a daily 20 minute walk aiming for one mile. Or break it into two or three walks. Outside air and sunshine plus movement helps. Do this even with lethargy.
4. Observe regular sleeptimes and if you nap, do it before 3pm.
5. Sublingual B-12, D3 and Magnesium and helpful for pain, cramps and focus. You might ask your dr for an anti-depressant which will help with focus also.
6. Each day, do something purposeful even if it is a household chore. Talk to a friend about anything else. Do something you enjoy.