Suggest Remedy For Headaches In The Back Of The Head

I have headaches that are centralized in the back of my head and radiate down close to my spine.When this is happening I will have moments where I can not do anything. It feels like a lot of pressure and that I have needles poking me in my head. It makes me completely stop doing whatever it is that I am doing till it is gone. I am constantly medicated. I am using tylenol all the time. Do you have any idea what this could be. I have been dealing with this now for a week and everyday it gets worse.