Fatigue can be a very difficult thing to live with, especially when you are busy at school and trying to carry on with your life. Fatigue in people your age can have several causes. You are correct in that anemia is one of the possibilities. If you are anemic, your diet is not likely the cause. If you are female, then the most common cause of anemia is having heavy periods, which can result in iron deficiency. The only way to tell for sure is to have your blood counts taken. Other possible causes of fatigue include infectious. For example infectious mononucleosis can cause fatigue which can be severe and carry on for many months. If you had a sore throat a while back that was unexplained and then went away, this may have been this infection.
Since there are many other possible causes of your fatigue, you should be evaluated by a doctor. I suggest you schedule an appointment with your primary care physician
or internal medicine doctor
). He or she can take a more detailed history of your symptoms, take some blood work, and perform a thorough physical exam. Hopefully, you can get to the bottom of these symptoms soon because you don't want to live you life feeling tired all the time. Good luck.