Honestly, I'm actually kind of the opposite, where I stay awake for a very long time and then I'm suddenly asleep. I fall asleep sitting up, I sleep with lights on, I've fallen asleep eating dinner, and I've gotten used to sleeping through people screaming at each other (mostly). My partner's even talked about how they're shocked that they'll be talking to me, having a conversation, and then turn back and find out I've fallen asleep. I mean I AM generally speaking, a night owl, but that's because night is when I get peace. Falling asleep randomly probably has to do more with just not sleeping when I should, I suppose, even though I... could.
So being the opposite, I guess I've been troubled by my lack of ability to fall asleep recently in a different way. Normally I can fall asleep any time because of my sleep debt, but right now my anxiety is wound too tight.
Feeling very sympathetic to your troubles though, it must be really hard to not be able to sleep at all and to struggle with that all the time...