I have had a headache right behind my eyes for about a week now. i have taken advil (ibuprofen) but it doesn't seem to even touch it. what could be causing this?

Inflammation: You could have inflammation of your sinuses or ischemic optic neurophy.Do not wait, you need to be seen asap.

Optic neuritis: Any changes in vision or double vision? Behind the eye pain (retro-orbital) pain can be caused by inflammation. In younger women, if accompanied by other visual symptoms can represent optic neuritis. Since the pain seems severe, you should see your ophthalmologist for a complete dilated exam to check for this and other problems such as optic nerve swelling.

Could be basic: It is possible that a more basic problem, such as sinus inflammation, or even dry eye syndrome are the cause. Of course, your eye doctor and your regular medical doctor should be involved in your care.

Not the most likely!: Retro-orbital pain that is bilateral, does not affect vision, can have several causes. Severe sinusitis is the most common cause, and certainly the least serious of the other causes proposed by my colleagues. See your physician.