Just curious, are you aware what your oxygen level is when you are sleeping? (Of course, you would have to wake up and check it immediately, or have an overnight test of your oxygen level.)
I am using oxygen only at night, although I can use it during the day. My oxygen level stays above 90. usually well above 90, during the day.
I had an overnight test done while not using oxygen and the level dropped to 82% at times but averaged 86%. I had no symptoms so was unaware there was such a problem.
My respiration slows and is shallow when I sleep, which I think is the case for people in general and that creates the problem.
Just something to consider. I expect your doctor has already and feels you are fine.