Why am i constantly getting headaches?

Im only 16 (about to be 17) and for the past week or so, its been massive headaches. Right before i go to sleep, to the minute i wake up..i dont eat much sugar, i dont like caffine, i dont like candy, i dont eat fruits (im allergic) i guess one of the reasons can be because i dont excerise or eat. I dont over work myself...except for the late night studying, but school's over..and its still happening. Ive been starting to get them for the past month for a week or so..on and off...and its starting a week ago again. I dont want to start taking pills before i get immune to it, and im usually by myself, so no one else is causing this...maybe i overthink all the time?