Why does the back of my head hurt by the end of the day and when i lay down on a pillow?

Tender neck a clue?: A common (if not most common) reason for mild, recurrent headache is tension headache. This refers to increased muscular tension about the head and neck. The melons we sport on our neck are relatively heavy, and simple movements through the day lead to fatigue on supporting structures. Pillow pain suggests cervical spine issues. Get checked, xray, CT or MRI? Don't mess around.