I'm so sorry you're going through this. I too started having constant terrifying nightmares unrelated to my first accident about 6 months post accident. We found my cortisol levels ran high at night and low during the day, hence the daytime fatigue. I think a whacked out circadian rhythm is part and parcel of PCS. I also found that sensory overload during the day (and not much) contribute to the poor, disturbed sleep. I use medications, supplements, and monitoring my activities and do ok most of the time now. I was diagnosed with PTSD because of this, but I'm not sure of this diagnosis. I just treat the symptoms. It is a terrible way to wake up in the morning.