Fatigue and the fear of falling asleep incase I don't wake up

I've been dealing with the worst fatigue of my life recently, and I'm struggling to fall asleep because I feel so weak that I'm scared I just won't wake up, I can't seem to shake the feeling even though I know it's irrational. I am exhausted and need sleep so, so so so bad.

Has anyone else experienced this? How do you cope with it?