Sometimes I take Melatonin. Our bodies produce melatonin so taking one tablet just adds to it and helps you relax. Of course, there are other sleep aides out there for more severe cases of insomnia. A few people I know take Ambien. I believe it is a prescription though.
I went through a bout of insomnia some years ago. Eventually it just stopped. I think it was stress related.

I know how it feels, and it's not fun. So I hope you can find something to help you. Good luck.