Why do i get dizzy spells alot?

I am 13 years old and i seem to get dizzy spells about every hour or two and it hasn't gone away since it started 4 years ago. I have noticed that i get dizzy when i stand up or lay down ( even though i get up and down slow ) , also when i turn my head left or right , when i jump up or down , if i don't use the restroom immediately , if i stay i sitting or standing up for too long , if i run , and also when ever i am in a big area ( such as a big empty house , a big empty arena , an empty field )...... i eat very healthy and exercise for about 30min-1 hr every day . I do around anywhere 1-6 hours of video gaming/tv a day. I take a brake every 1 hr and the next hr i go back on. I have been to 4 different doctors/pediatrician in the past 4 years and i have gotten my blood work done and they all tell me that my blood is fine and something else me the same thing , to eat more healthier , stay off tv and to exercise more, if tried to do it but i still get dizzy. But that cant be the problem. it has to be something else. I have gotten used to being dizzy but sometimes it gets to strong and i go to the hospital . i need help desperately