I was getting this problem too. It was sporadic, but geting worse untill I found the problem completely by accident:
I used to use Sudafed heavily because of alergies. I stopped taking it since it wasn't doing much for me anymore, and all of a sudden my problems were gone. I have a friend who's ex has the same trouble, and guess what? He's on the stuff 24x7 as well. If I take it for more than 2 days, I have trouble staying up unless I'm fucking. Needless to say I don't use it anymore.
Don't know if you use the stuff, but the point is that it could be something simple like this. FWIW.