For that much fatigue, I was expecting a killer commute. 7km should just be a blip and not noticeable under normal circumstances. There's lots of advice about a hearty meal but for 7km, I'd sure hope your body has that in it without eating anything. As others have mentioned, first focus on getting adequate sleep, and if that doesn't solve the problem, I'd vote with sci_femme: when was the last time you had an annual physical? Something just doesn't sound right...