I don't know, but I'm still awake! :(
It happens all the tine.
I have the same issue. A product of being bipolar. I have to take three sleep aids to knock me out for six hours sleep. Sucks
Humans aren't designed to go from mental activity to sleep in a matter of seconds. For an hour before you want to sleep start winding down. Read a book, watch some TV. Get off the damn internet.