Why does my head hurt when I wake up early?

I think it has something to do with cigarettes...yeah yeah I know theyre bad but every time I need to wake up early for something my head feels like its about to explode. I always wake up with a huge headache like no other, it hurts so bad it almost feels like my ears are involved. But whenever I get a good amount of sleep like 10-12 hours then my head doesnt hurt at all and I dont feel like I need a cig but when my head hurts that cig is coming out and my head usually feels better after that. But why is it only when i wake up early than usual that I CRAVE my morning cigarette?