Have you tried going to sleep at 10 and waking up at 6? It sounds obvious, but you'd be amazed at how many people never do the obvious thing. Like forgetting to plug in a computer and wondering why it doesn't come on when the power button is pressed.
Yes. Spent a month in a ward with a fixed regiment. Never got used to it, and my sleep cycles were all over the place. By the end of the month I was starving because I was missing so many meals, and it was overall torturous.
If you have the means, you might want to consider seeing a sleep specialist and having a sleep study done.
There's a lot of things that can cause irregular sleep cycles like that and a sleep specialist can see what your brain is doing while you're asleep. That helps you and your doctor figure out a treatment plan depending on what they see on the results.
I checked and it seems like in my area they only do checks that I already know the results of. Stuff like SpO2 analysis, or checks for snoring and sleep paralysis, which I don't have any problems with. I figured that I'm just drifting towards sleeping at somewhere around 6AM with the morning sunrise, and in the last years it was consistent across different time zones. I'm usually completely fine and working around this, and my workplaces thankfully had been quite loyal to me being consistently late as long as I got the job done, for which I always stayed last. It's just the stuff that is built for morning people that throws me off hard, like appointments at 9AM that I can only realistically meet by staying awake even later.
Oh man that sounds rough. Sorry the specialists in your aren't equipped to check your REM cycles and things of that nature.
It sounds like a frustrating situation to live with and I'm not sure I have any advice other than ask your doctor about shift work disorder.
What you're experiencing sounds very similar to what happens to people who work 3rd shift for a long time and can't get their sleep schedule back on a day time=awake schedule.
Sleep issues are incredibly complex however and its something a doctor who has your medical history can better address, but having some terminology to describe your symptoms can help them help you. I hope you find a solution soon