First thing I would look at is sleep: Are you getting enough of it? Most of us need 7-8 hours. Some need more, some need less.
The second thing is your diet: Are you eating enough to support your level of activity? What's your current calorie intake, and your current calorie range?
The third thing is your exercise: Are you overtraining? This article explains some of the signs of overtraining: www.sparkpeople.com/resource/fitness_artic