Still haven't answered my questions...so I'll presume you never sleep at the same time each night and you have no routine...

First, get more active during the day. Even if it's simply going outside and walking for a while. Exerting yourself allows the body to produce more sleep chemicals on its own.

Second, get a sleeping routine down. Even if you don't sleep the same time each night, do the same things before you go to bed (shower, brush teeth, etc). Doing so will create a mental trigger to start your brain into shifting down for sleep.

If after a couple weeks this doesn't help, try adding Melatonin to the mix, half an hour before bed. It's natural (the body produces it to regulate when you feel the need to sleep), not habit forming, and it has no side effects save for drowziness and the chance of your body compensating for the spike in chemical levels (I'll get to that in a minute). When you add Melatonin to your sleep routine, it can teach the body to produce more Melatonin when the sleep triggers start (a la your nighttime routine).

After a couple weeks you may notice that the Melatonin is working less. Now is the time to raise your dosage, and start staggering when and how much you take. Doing so will keep your body from being able to predict when the spikes occur, thus preventing your body from either building a resistance to Melatonin, or simply producing less.

If the Melatonin doesn't work on its own, then you'll want to add a sleep aid. (( Avoid Ambien if you have any issues with hallucinations, as it will make them worse. )) This is something you'll need to discuss with your dr.