Well, first of all, I’m sorry you’re suffering. I too, was in your shoes and had awful fatigue, brain fog, stuttering, body tremors, loss of taste/smell (still have that). My general practitioner finally diagnosed me after a year with Long Covid. He didn’t run any tests, just said by my symptoms that I have it. I began doing my own research on how to heal and read that pacing would help the fatigue, so I began walking around my house, then for short periods on my treadmill until I worked up a 3 mile walk. It took a while, but I now am walking 3 miles, 3 times per week and have added light weight training. I also had 7 Stellate Ganglion Block Injections. The 7th one took my body tremors away. I still experience some anxiety, but nowhere near how I was. I would suggest to you, since you know your heart and lungs are in good shape, to start walking a bit every day and stretch it out every other day or so. It’s the only way you’re going to get better. Much luck to you!