Actually, don't try to stop yourself from thinking, it'll just stress you more. If you're not wanting to do pills or anything, try some meditation techniques. Think of a symbol you find particularly pleasing and trace the outline/contours of it with your mind repeatedly. It's not so much about emptying your mind as it is focusing it to the point of lulling yourself to sleep. It sounds like you're so worried about sleeping that you're waking yourself up to see if you've slept. I do that before traveling. Another thing you could try is look into lucid dreaming. There are tons of meditation techniques for that and they put me to sleep like nothing else.
