I have nights like that sometimes. I guess I get too tired to sleep or something! I try to make myself go to sleep so I don't bother the DH. The kids sleep pretty heavily. DH is a heavy sleeper, too, but if I'm not in bed beside him, he doesn't sleep well.
Here is a tip: Try audio books! They are better than reading at night bc you can close your eyes and relax a little instead of trying to hold the eyes open. I thought I would hate an audio book, but a friend let me borrow one a few years ago. Now, I am hooked! I like the tapes best bc you can stop them where you want and that is where they are when you turn it back on.
Also, I get SO SLEEPY when I listen to them....and usually doze off. Then I have to find my place the next night. LOL! but it does help me sleep, so that's the point I'm trying to make!
I also use headphones only for this so it doesn't bother anyone and so the kids don't hear a "bad word".
It is actually so amazing how little sleep humans can really function on! i haven't slept for years. Not very well, anyway, since the first baby was born.