I'm not sure what the problem is here. Are you afraid to die (i.e preoccupied with your bodily functions stop working)or is it something else that bothers you? Do you associate the bedroom with something unpleasant?
It could also, as MrGreen pointed out, be a bad habit that has to be broken and that you've learned to feel anxious without any good reason for it, and need to distract yourself from this pattern of thinking.
If any of these answers don't appeal to you, I would recommend to talk to a doctor or therapist about this.
Nora
Death is not worth a worry. Just think about how far you have made it so far in life. And you have slept, no doubt, many many times. You need either a distraction to get your mind onto something else, radio, tv, small light on, etc, etc or even some exercise last thing at night. To use up your energy. The same energy you waste with worry about death. There is no miracle cure. Only you can change your thinking patterns. Or change your surroundings so you wouldn't think as much.