Melatonin worked for me several years ago. I tried it again more recently and it had the opposite affect on me. It actually made me have the problem you are having now. I'd wake up in the middle of the night and not be able to go back to sleep.
I NEVER sleep through the night. EVER! Sunday night I went to bed at 8:30 and got up at 5:30, but woke up several times. Last night I went to bed around 11:30-midnight and woke up at 5am. I think your body gets used to less sleep eventually. It's not fun, but I've adapted.
The best nights sleep I've had in a long time was at my moms when it was just ME. Bruce wasn't there and neither were the dogs. I slept SOOO good!

I agree with the exercise idea. I should try it sometime too.