At least you're falling back to sleep. That's a good thing. But it still stinks.

I can go through bouts of that too. Sometimes, too, my body clock decides to reset itself. I used to work a lot of midnight shifts. I'll end up finding myself drifting back in bedtime because I can't fall asleep. Or if I do, I wake up just like you're describing. The only thing that helps me is to stay awake for about a 24 hour period. That seems to reset things.

Have you tried getting up in the middle of the night for a while and just doing quiet stuff like reading or writing? When that used to happen to me all the time (after my car accident), I would get up and get a nice cup of herbal tea and read. I'd be up a couple of hours and then go back to sleep.

Hope you get it figured out! You may need to be creative.