I have had sleep "issues" most of my life. I slept walk from almost the time I could walk. my parents had to strap my feet to the bed at night. I almost got out the front door when I was 6 years old. had to take my doll for a walk
I had bad night mares when I was young and in my early teens had sleep terrors. I slept "normal" otherwise, liked to sleep in and I slept well and deep and woke up rested. My 20's and 30's I slept great, still had vivid dreams but nothing horrible, could sleep though the night wake up alert, sleep though noise. When I was in college my apartment was next to a rail, train looked like it was going to run right though my bedroom. Now one little hoot from an owl can wake me up!
When my sleep started to go I just pushed myself harder with coffee and sheer will power, if I could have do over I would have made sleep more of a priority.
I know that my circadian rhythm is off as well. I was always a night owl who loved to sleep in. After I returned from my first trip to India my clock was inverted and never went back. Now I want to sleep as my fatigue gets worse around 4ish then I start "barely" but notably waking up around 10 pm My pain is worse at night and I am wiped out but I am rarely really super sleepy.... unless its late afternoon. naps don't make me feel any better and they make the night even worse.
I agree that its complicated. but it is still interesting how many of us have similar challenges, not everyone in everyway but enough to make you realize its not all in ones head.