I rarely get headaches, and the frequency and type didn't change with the onset of ME. I think ME affects brain cell function in regions unique to the individual, so any sort of neurological disorder seems possible from ME, including headaches. Likewise, ME can affect the brain cells or nerve cells involved with gut function, resulting in a similar wide range of individualistic symptoms.
That brings up a related question: do PWME report a variety of heart dysfunction that might be attributable to ME? It seems logical that there would be. Eyes, ears, nose, and tongue show those sorts of variable dysfunctions; are there any other body parts with significant neurological interaction that show or don't show this effect?