It could be any of a number of things, though I would bring it up with your doctor. For the last 10 or so years, I had been existing on any where from 2 to 8 hours of sleep a night, mostly 2 the 8 every now and again.

I know with me, my brain can not let go of problems and does not stop for anything. And that would wake me up a lot, lay down and up in 2 hours ready to go. It was not until last year when my doctor put me on Mirtazapine, which is supposed to help with my depression, that I actually started to get a consistent nights sleep. And even now, when I run out because my refill has not arrived (I get them from the V.A in the mail) I am right back to 2 hours sleep. But lately I have started to wake up every couple of hours but able to go back to sleep.

Which in it's self can be rather interesting, one of the possible side effects of the medication is to hallucinate, which has happened to me a couple of times.

But I guess it could be from all that you mentioned