Sleep is the most insane part of PTSD. Good...good ...good....not good (and no reason why)I will almost fall asleep and then jolt awake just before drifting off as a sort of protection from the nightmares/ dark mental states I am afraid of falling into. If I had more time to process it all then I think I'd let it happen but my new job has me working crazy hours with a 5am wakeup and I just can't afford to collapse into my feelings.
All I have learned is - the one thing that's hardest to do is the one thing you need to do.....don't worry about sleep. It's hard to do but its on top of the list. The more you ruminates on not sleeping and nightmares the more sleep doesn't happen and nightmares do.
Go here and read the PTSD Cup article. Fill your head with grounding and other things. It may not always work but it sure helps......