I have a dull ache on the left side of the head sometimes on the left side forehead. the pain isn't bad enough for otc medicine. for over a week now.

Many causes: There could be many things causing your mild headache: dehydration, sinus infection or allergies, migraines, sleep deprivation, muscle spasms, stress.... I would try pushing lots of fluids, getting plenty of sleep, taking 600-800 mg of ibuprofen (if you don't have any stomach or kidney problems), and reducing stress. If it still continues, see your doctor.