I can give you a quick run-down on sleep aids from both the stand point of a medical professional with a background in pharmacology, and a nearly incurable insomniac of over 15 years.
Prescription drugs: I've tried ALL of them at some point or another. The ONLY one that doesn't carry a list of potentially serious side effects, won't ruin your waking life, doesn't carry a risk of delirium and sleep-walking, and is still effective for long term use is trazodone. The only negative side effect is that it decreases your libido if you're on a high dose of it, but that effect disappears after 24 hours from stopping it. I would stay FAR away from the "Z-class" drugs like Ambien or Sonata. Tried them, and had nothing but nightmares. There are plenty of horror stories about people waking up in their car driving somewhere, or wandering around outside on those. And I've personally seen a lot of weird behaviours out of people using it in the hospital. Plus, they're only effective for the treatment of short-term insomnia. The benzodiazapene class (Restoril, Valium, Xanax, Ativan) etc are frequently used for sleep aids, but are habit-forming after a week or two. Trazodone can be taken "as needed" without having to be on it every day, it's been around since the late 60's, and has no apparent long-term side effects - it's the only prescription drug I could recommend.
Over the counter: Benadryl is perfectly safe, but becomes ineffective quickly (like after a few nights in a row). Combined with melatonin, it's not bad. Melatonin is something your body naturally produces which allows you to descend into the lower levels of sleep that insomniacs have difficulty reaching. The more restful/healing levels. Your body doesn't produce enough of it if you're stressd (Prednisone mimics the direct effect of stress on your body in every way - it's deliberately suppressing your immune system, and tends to stimulate a stress response on your central nervous system.) or if you have a less than dark/quiet room to sleep in. Blue light exposure (like TV/computer screens, night lights etc) before or during sleep will decrease melatonin production as well. Unless you're really sensitive, melatonin supplements won't do much on their own. In conjunction with something that knocks you out, like Benadryl, they make for a restful night's sleep.
Alcohol, marijuana, opiates - all have an effect of putting people to sleep, but they disrupt your natural sleep architecture to where the sleep you're getting isn't restful. It's akin to somebody with sleep apnea - they may sleep soundly all night, but the sleep is essentially useless to their body.
If I were to recommend a sleep aid to somebody, I would suggest 25mg of Benadryl and 3-6mg of melatonin together. Along with a quiet, dark room. Even Benadryl will disrupt the normal sleep cycles to some degree, but in low doses and in conjunction with the melatonin, it at least allows some normal sleep.
I feel for ya - I've been an insomniac since I was a teenager, and haven't slept unmedicated for a very long time.