I have been taking Melatonin for years. In addition to helping with sleep, some research has shown that it might be a cancer preventative. It helps me fall asleep but has a very short half-life so does not help me stay asleep. Additionally, I've read that it's important to turn the light off soon after taking it, so don't take it too long before you intend to go to bed.

When I had serious problems sleeping after the death of my father, I got an Rx for Lunesta and later Ambien. They worked wonders (out like a light!), but I got horrible rebound insomnia when I stopped them. Only lasted about a week, though.

Nowadays I do take one 25 mg. Benedryl (same thing as the Zzzzyquil now available) when I am having trouble sleeping -- mostly due to stress/anxiety -- it works better than melatonin but not as well as the prescription stuff. It used to give me a hangover until about noon the next day but doesn't seem to any more; perhaps I have built up a tolerance? I have mild asthma and have never been warned off it by my doctor, nor does it seem to make my asthma worse.

Good luck -- insomnia sucks!