Probably long covid.
Probably long covid.
Anecdotally I was having a bunch of bizarre symptoms this summer and thought I had long Covid too, and ended up in the hospital due to heart complications which turned out to be from Lyme. They treated me with the standard antibiotics and I’ve been pretty much fine since then.
I've not even a health anxiety person. At this point I'm sort of thinking "it is what it is". I'll continue to live life. But the only thing there really is to point to is either covid itself, or some vaccine response.
Your symptom cluster is very similar to me since a long long time before Covid.
I've seen perfectly healthy people—before and after COVID—who literally had their life changed due to a completely random infection or issue. People who went deaf after having a baby or developed T1 diabetes. Some people were "perfectly healthy".
But some people seemed healthy until they weren't. One day, their eating/drinking/smoking habits caught up with them due to age or complications from things they didn't even realize were health problems until it suddenly became an issue.
I am not a doctor... but you mentioned weightlifting... the fatigue and neck pain could be a pinched nerve? Perhaps an injury that manifested itself after a viral infection? Have you seen a physiotherapist? I finally saw one about arm pain and it changed my life.
Well, hoping you find some answers, then.