Keep trying the melatonin. I forgot to mention you should look for the kind that is in a fast release capsule, the slow release never worked for me. It took a few nights before I was sleeping good using it. There is some support for the idea that using it over a period of time (such as over four weeks) may be more effective than taking it one night only. I still wake up sometimes, but I feel it is working for me.
Sorry your still not sleeping good, that for sure helps to keep the stress level up there.
Other natural things I tried over the years for my problems with sleeping are:
Valerian, magnesium, chamomile, kava, tryptophan, and 5-HTP(which is like melatonin). The all seemed to work for a while, like up to a year or more, but eventauly I started waking up after just a few hours of sleep just like yourself.
I even read once that you can use catnip, passionflower, and hops as sleep remedies. (I agree with the Hops as in Beer!!!)
Find yourslef someone local in your area that is into all the herbal stuff and they may be able to mix a few together for you. Or try another thing that I have been doing for the last few months, and that is keeping a journal that I keep track of all the nights that I did sleep good and what I did different that day or night. It also helps to clear all the crap out of my head before drifting off to sleep by writing down all the crap I am thinking about and making a list of what I want and need to do tomorrow. That way I am not laying awake all night thinking I may forget something I thought of. Keeps it less mental that way.
Hang in there and keep trying new things, but stick with one for a while and give it a little time to kick in.