I'm sorry to say that I have no idea... I'm in the same situation, only my preminitions come durring my waking hours... it's a tad anoying as the only type preminition I ever seem to have are death preminitions. I'll get them at completly random times, be it when I'm in the shower or when I'm in the middle of talking to a friend (these are the worst, hard to explain that you stopped talking cause you just saw someone being sliced open in a park).
But I've gotten used to it... I only wish I could help you.