In reply to Sharp:
> You spend5 minutes explaining you don't have trouble falling asleep but you wake up early regardless of how well you've slept and they say "just don't stay awake in bed more than 15 minutes." And you say, "but I don't have trouble getting to sleep"
I think the point is, that if, say for example, at the moment, you are sleeping for 4 hours, then if you force yourself to stay awake until 4 hours before the time that you WANT to get up (so for example, if you want to get up at 7am, you don't let yourself go to sleep until 3am), then because your body is used to sleeping for 4 hours, then you are pretty certain to sleep all the way through - after all, you will be knackered, having stayed up until 3am!
You will still get your usual 4 hours sleep, but without the frustration of waking too early. So they are trying to answer your 'waking too early' problem, using advice that they do repeat because it does work.
Also - what times do you get up when you are not working? Do you try to stick to the same time, 7 days per week?
Another thought is what screens are you looking at? The blue light from screens (tv, tablet, computer) can disturb your sleep rhythms, so it might be worth trying to cut your use and do things like read paper books instead?
Also, you don't say if you have been taking naps during the day or at weekends to try to catch up at all? You really want to avoid doing this as once again, this will just interfere with your sleep patterns
Finally, there are loads and loads of resources on the web with all sorts of good ideas.
Good luck - it's very frustrating.