Enormous fatigue on day 6 after wisdom tooth removal, and two exams in 3 days 😭

I have two PhD candidate exams in 3 days and I’m literally falling asleep every minute, have no energy to study, and it feels like someone dropped a hot elephant on my head and eyes - they feel so heavy and tired like I didn‘t sleep at all. 

What I have: 

1. One upper wisdom tooth removal. 
2. Slight pain, discomfort and some jaw pressure.
3. I have enormous fatigue and a bit of runny nose and slightly raised body temperature (no fever though). 
4. I now eat same as before, though no hard solid food, so it‘s definitely not the cause of my fatigue.  
5. I take one 400 mg Advil once a day.
6. Stay hydrated.
7. Rinse my moth well salt and baking soda every time after food.
8. Extraction cite now looks like dark big and empty hole (no pain). Why does it look empty?

Why do I have fatigue and slight flue-like symptoms on day 6 considering your healing process was as it should be? 

Can anyone suggest anything that can safely boost my energy level and focus for the next few days?