I should mention head pain in relation to alcohol hangover, which was not like before ME. In ten years undiagnosed there were a couple of occasions where I just said to hell with it and overindulged in the hope it would anaesthetise me a bit.
During hangovers which follow such folly, as it didn't help, I felt head pains I would describe as punctate cutting pains, like pins being stuck in my brain, ie within the skull, same kind of sensory space as headaches.
These are distinct from other pains I get in that region, planar cutting pains, which often accompany phantosmia of very dry astringent chemical odours and suspected viral recurrence. These are flat planes of pain which also give a sensation of cutting, e.g. as if a large flat blade was cutting horizontally through my "brain", symmetrically, which might imply brain linking structures like the corpus callosum or midbrain. These persist as long as the viral episode and then depart when it ends.
So something is going on with pain receptors, apparently mapping to the brain, being stimulated in different ways by these two phenomena. Before ME I never had such cutting pains. Goodness only knows what is really going on in there. Never had an MRI.