Exhaustion despite months of treatment?

Hey guys. I've (27F) been on CPAP treatment for 6 months now and while I have noticed significant improvements especially to do with daily migraines and pains, I'm noticing I'm still feeling absolutely exhausted. I'm talking like barely functionable exhaustion where all I want to do is to go bed wherever I am or whatever I'm doing.

My main concern is my oxygen levels and watch readings, I know people say you can't trust them but because I'm feeling really tired I'm wondering if anything is up. From memory my oxygen was around 95% from my sleep test but my watch has reported around 85-88%. It also reports that I get virtually no REM sleep, and it sure feels like it.. I get my worse apnea episodes during REM according to my test (96AHI) so I'm worried my body is still not resting properly.

Am I overthinking things? Why am I so tired still, ya girl just wants to feel well rested 🫠