Wearing glasses for too long gives me a headache i usually wear contacts all day and then glasses at night when i get home until i go to bed. some days i wear glasses all day long. on those days i get a headache. any idea why this could be happening?

There : There may be a problem with your eyeglasses, e.g., the optical centers of the lenses may not match your pupil location, or the eyeglasses may no longer be the correct prescription. A comprehensive eye examination by your ophthalmologist would be the best way to determine the cause of the headaches.

Headache: I would be suspicious that your prescription in your glasses may not be correct. Dry eye can also cause this issue so you could try using some artificial tears. See an eye doctor for further evaluation.