Can't Sleep! Please Help!

I know someone's probably covered this somewhere already, but I can't find it anywhere, and i'm getting desperate. Basically i'm having a lot of trouble falling asleep, and on two occasions - about a week apart i've not slept at all. I don't feel stressed, as i've lost sleep in the past due to stress so I don't believe the problem lies there. I eat healthilly, my diet includes lots of fresh fish, rice, vegetables, and fruit. Exercise - I admit I don't do enough, but the lack of sleep has only started recently in the last fortnight. My sleep pattern is fairly solid, I don't have too many really late nights followed by early's, but even then I find I can usually fall asleep after a while. Recently, however I just have so much trouble falling asleep. Also i've noticed that when i'm having trouble falling asleep, my heartbeat's harder, and I feel really hot.
Can someone please give me some advice about putting myself to sleep (without pills). I've tried herbal sleeping pills, but no joy.

Thanks