The recording pulse/ox meters stay on while you sleep. They can alarm you when your Ox drops or just record you Ox levels while you sleep. You can be breathing continually but not breathing deep enough. The meds relax muscles. Maybe they are relaxing too much and reducing the depth of your breaths.

I use a very floppy pillow that I bunch up on the right side of my head. It usually works for me. I have no lift to my head. The back of my head is almost on the mattress.

I get some of my best sleep in a recliner. My wife gets good sleep by not hearing my breathing or feeling my twitches. It takes a lot of experimenting.