I also have sleep apnea which took far too long to diagnose as I assume all the docs thought my fatigue must be from my depression, I use a CPAP machine every night
theres a common doctors thing to assume that all depression and anxiety sufferers cant be suffering from any illness that comes from a physical cause
I should have also mentioned that if you fight back against the anxiety, and are mostly tensed up anticipating it, this will make you very tired
best to relax, accept and float thru it
'float dont fight'