Lyme is negative but we all know the problems with a correct Lyme diagnosis.
Although my CD57 is low with 28.
Even knowing if a chronic virus is active or not isnt possible. Ebv is known to reactivate especially if immune system up the creek. Hhv6 is another common virus in cfsme.
Your right about lyme but many other bacteria also hard to find.
A dodgy immune system any infection is possible or combo of infections. Sometimes certain treatment trials can be helpful. People have tried antivirals for several months, if it helps great if not then move onto the next thing to try. Even broad spectrum antibiotics like doxycycline may help as well as lead to a diagnosis too and maybe broaden bacterial treatments.
Generally its not one thing going wrong in cfs, along with infections and immune function, dysfunctional hormones can have an impact. Also orthostatic issues can be worse for some more than others.
Personally i do well using a number of anti infective agents and hormone replacement. But i would be screwed without treatment for sleep but thats me.