This happens to me, too, but I'd gladly trade all the good ideas in the world for a decent amount of sleep!
Starting from about age 12, but definitely getting worse as I get older, sleep is something I just can't seem to get right, no matter how I approach it.
I've tried getting eight hours of sleep, and it doesn't work. I do pretty good on six hours, but only for a while. Over the course of a few weeks, six becomes four, which becomes three, which is then two, and suddenly it's 3 days later and I'm still awake.
When it gets to the point that I find myself getting less than four hours of sleep a night, the only way I can force my body to sleep more, despite being very physically tired, is with medication. Of course, most sleep aids can't be taken for long periods of time, so that only helps for a short while.
Sometimes I don't get tired until 4am, and other times it's all I can do to stay awake at 6pm, regardless of whether I got up at 6:30 in the morning, or noon.
I've tried enforcing a rigid schedule, meditation, exercise, various sleep aids, antidepressants (Pazil, Zoloft), just "going with it", and as of late, melatonin supplements at the recommendation of my doctor. They helped for a few weeks, but then that, too, stopped being effective.
The closest I get to a normal sleep schedule is that about half the time, I can go to sleep around 4am and get up at 10am - but that's not really a very practical solution and there are 3-4 days a week where it's just not at all possible from a logistics standpoint.