could be your eating habits, maybe your not getting enough iron, ive had the same problem but it is always good of course to get it checked to make sure its nothing too serious! Hope you get better soon!
I'm 17 too and get dizzy a lot from excersising. I went to my doctor and he told me to drink more water and that I was probably dehydrated. When I went he did a few simple tests on me so I would go to your doctor and see what they say if drinking more water doesnt help.
You could have anemia that's what it sounds like to me try taking some iron supplements or have your doctor check your hemoglobin levels most offices can do it right then and there with just a little stick to the finger
Welcome to the MedHelp forum!
Extreme fatigue could be due to anemia, diabetes, hypothyroidism or due to liver problems. In women polycystic disease of the ovary too should be ruled out as it causes insulin resistance and fatigue.
Another possibility is sleep disturbances. You need sleep studies to rule this out. Do discuss this with your doctor and get yourself examined.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!