I have the Post Covid Fatigue and I am sleeping 10-11 hours at night and then some afternoons 2 -3 hours. I have found that if I get a sore throat I have done too much and it is followed by the tightness in the chest. It means I have overdone it and I need to lay down and rest or sleep until it goes away. It may take a day or two but it does goes away. All of my chest x-rays etc also came back normal. I found a post-Covid Clinic near me and have signed up and am on their wait list. You need to rest as much as possible. You don't want to push it to the point where your chest hurts because then you are not getting better your body is simply fighting off more of the symptoms. You want the symptoms to completely go away. The infectious disease doc put me on another anti-viral although it is too soon to see if it is working. I hope this helps and Good luck. You have to work with the energy you have and try not to go beyond it.