What causes a constant headache encompassing entire head. Has lasted about 8 months?

What causes a constant headache encompassing entire head. Has lasted about 8 months?
I have had a constant headache, every day, all day, for about 8 months. even though I lean over it feels like someone hit me with a club on the forehead. At times the headache becomes more severe and then tapers off. Have had CT, MRI, CT angio, all negative. Have tried numerous medications both prescription and OTC without any success. Do not have blurred vision. Do have hay fever type allergies.

Best answer:

Answer by ps@yahoo
What about getting your eues tested, could be bad eyesight causing this headache, its not normal to have a headache for as long as you have.Make an appointment with the optician lol.

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