Hello Aposiopesis: I presume you're following all of the recommended practices: getting enough exercise, avoiding caffeinated beverages, staying off of your computer, phone, tablet, etc. for at least 2 hours before bed, etc. Those sorts of recommendations, & more, are easily found on-line. I have read that it is possible to become so tired that it can affect one's ability to sleep. Perhaps that is what's happening to you.

Another recommendation is generally that, if you can't fall asleep within 20 minutes (I think it is), get up & perhaps read a book or magazine, maybe listen to some soft soothing music. I've also read that drinking a cup of warm milk before going to bed can have a soothing effect. (I haven't used that one.) Are you on any med's? Sometimes medications can cause a person to have difficulty falling asleep & staying asleep.

I sometimes have difficulty falling asleep, or getting back to sleep if I've woken up. What I sometimes do is to get up & do sort-of a walking meditation... sometimes for as much as an hour or two. I walk around-&-around our dark & quiet home. I focus gentle attention on each foot as it touches the floor. Thoughts come, & thoughts go. I allow them to arise & fade at their own pace. When I do finally go back to bed, I almost always fall asleep pretty quickly.