Repeating Dull Headache Lasts 20 seconds

Has anyone experienced the type of headaches I started having two days ago?  Specific pattern is a dull interior pain which hits for a split second at the crown of the head just to the right of center, folowed 8-10 seconds later by a steady pain lasting 20-25 seconds.  Pain is about 2.5 on the pain scale of 1-10 (I know it is there but it does not affect my functioning in any way I can perceive).  Cycle repeats in periods as short as 2.5 minutes to as long as 6 minutes, with an occasional miss or two.  The periods are consistent for at least a half hour before changing.  I would liken the pain to that of a small muscle cramp - there is a momentary sense of relief when it ends.  The pain seems unaffected by anything exterior. It is unchanged by visual stimulus, light or dark, sounds, touch, level of activity, diet.  I have been taking the same blood pressure and cholesterol medications for a year since the last adjustment.  I exercise regularly and am in good physical health.