Make sure you're not dehydrated. Drink water, even if you're a bit dehydrated you would feel fatigued. PLUS - alcohol dehydrates you, and dehydration is the cause of hangovers. I came home from a club last night, drank 2 liters of water, went to bed. woke up completely refreshred...and an insane need to take a leak. DRINK WATER.
Also, get the supplement CoQ-10 it is a chemical that is used by every single cell in your body. Patients with chronic fatigue syndrome that take that supplement show significant improvement. Personally, I take many supplements (if you want to know which ones and why, feel free to PM me), along with CoQ-10. I average 5 hrs of sleep throughout the week, and if i feel tired a 30 min power nap refreshes me completely. I highly suggest you buy some, will do nothing short of improving your health.