A headache for around 3 days?

I went over a friend's house for 5 days and we've been on the computer for continuous hours. Ever since I got home I've had a headache and I felt dizzy. It stings to look at the computer and its hard to concentrate on looking at things. I've been drinking more water and I've been staying off the computer and I havent been watching Tv. When I go to bed it goes away after a little while of staying in bed, and then when I wake up I dont feel a headache, but after an hour or so I feel it again. I never get headaches..And Im really worried, is this something serious? Btw Im 14. Please and thankyou! <3