Insomnia is just sux. I really think the more you fight it the worse you make it.
Can you get into a relaxed state by just lying down casually and staring into space or letting your eyes unfocus? That's the next best thing to sleep and sometimes it even leads to sleep. I'm sure others have already recommended herbs and homeopathic substances so I'll refrain. I don't know of any good ones anyway.
Take care