Suggest Treatment For Headache Caused By Smoking Weed

Hey, Ive been smoking weed for years and just recently its gotten to become a big problem. I started getting headaches from it over time so I quit. After three months I still get radiating pain form the back of my head. I went to the doctors to check it out and they gave me a ct scan bu nothing out of the ordinary came up. The pain is still there and its becoming almost unbearable and Im pretty sure it was caused by the marijuana. Is it something neorolgical and what should I do now?