ok. instead of trying to get to sleep straight away, try not to focus too much on it. Occupy yourself, do work, or preferably, something more relaxing, until say 12 or 12:30 - (this is just to start off with - as you start sleeping earlier, you can move this target earlier and earlier), and then try and sleep. What I'm thinking is because your body is used to being awake at this time, it won't start shutting down for you until later, and flat blantantly refuses to go to sleep. If you leave going to bed until a little later, when you should be more tired, your body is more likely to listen to you, and you'll get to sleep after a shorter amount of time. As you train your body to do this, make the time earlier and earlier.
Try and get into a routine. I hope some of what I've said has been useful, sorry if you've already tried all this. I really hope you're able to sort it out, it's so mentally draining being tired all the time. I'd definitely suggest going to the doctor though - even if you tell him that you don't want to take sleeping tablets, he might be able to suggest something else.
Take care x