Hi Paula, I live in Colorado at about 5,300 ft. and also have long-covid and some of the same symptoms you have. A few thoughts--hydrate like crazy before you travel and when you're here and bring a finger pulse ox with you and check your oxygen if your symptoms worsen. I went to higher altitude in CO this summer for vacation and took it slow, went on very mellow hikes, rested more, etc. At one time when I went on the mountain, I didn't feel well, checked my O2 and it had dropped into upper 80s, so I went down to a lower altitude and felt better. Just wanted to share my experience with you. Maybe ask your doctor too about a prescription for altitude sickness to take preventatively, given your current symptoms and ask about vitamins or supplements to help at altitude too. There's a powder called "Acli-Mate", you can mix with water I really like. Best of luck!