I had this problem for almost 2 months after my MVA (motor vehicle accident).
Notice that i did not mention "concussion" because no doctors have confirmed or even come close to this diagnosis even though almost all symptoms i have points to PCS, plus with the guidance of the good people here like Mark and Bud to name a few.

I found something helpful when i was travelling in Vietnam and its called "Lotus Plumule". Its drank the way tea is and when i tried it for the first time i had the best sleep for the first time since my accident.