Probably a brain tumor, nothing to worry about of possibly being enlightened or starting to awake into cosmic uniteness
Being serious, try different diet, leave out something of your diet and wait couple of days, if it won't work, leave out something else; repeat that
untill you hopefully find out the reason what was the cause of the ache. If that doesn't work, go into a brain scan.
-v
[edit on 24-11-2009 by v01i0]