The back top of my head is very tender and has been constantly hurting for 3days now. it just started hurting up front today. what could it be?

Several things: This is a problem that requires a face-to-face meeting with your doctor. In that meeting, your doctor will listen to you, perform a throrough examination and possibly order labs or other tests. Based on this information, he/she will be able to tell you what's wrong and what to do about it.

Shingles: If there is no history of trauma and the area is tender to the touch it could be shingles. Call and make an appointment with your primary care doctor.