I replied similarly to another thread launched maybe three/four weeks ago, but I'll try to help:
COPD, failing or occluded/calcified aortal valve, mad mitral valve...these are all possibilities that can make the heart inefficient to the point where you realize you've really lost a lot of ground with your physical capacity for 'work'. There are other possibilities, but I wanted to give you a hint of how many ways the heart can be all but fully prevented from oxygenating your organs, your skeletal muscles, and......itself.

Sleep disruption is one deleterious effect of sleep apnea...doesn't matter the kind. But, will poor oxygenation of the body, you go into hypoxia or acidosis, or hypercapnia....all of them, really. Your body will want to go into the fight-or-flight response which is an arousal response. Who could sleep under that process?!?!?

If your sleep is disrupted often, and you don't or seldom get to the REM stage where you dream and get really good rebuilding going on, you should expect to have brain fog during the day, want to fall asleep as soon as you sit, be irritable, make cognitive errors, perception errors, and so on. You say you 'slept' 9 hours. Did you really sleep, or was that just a total of nine hours that you didn't realize had passed, but you were tossing and turning, awakening just long enough to start breathing again, and generally were not really resting? I have had long nights when I felt I had slept well, only to look at my Galaxy watch's report and see that I had a lot of awake time, or light sleep and not the deeper more restful sleep. The total was great, but the quality sucked.

A CPAP machine, of the correct type (they vary in what they are meant to treat by virtue of the software loaded into them and the algorithm they use to be a contemporary assistance with each and every breath you take), with the correct settings for the correct treatment, based on a correct diagnosis (this can be tricky even for the experts to get right), and with the best mask for your face and the way you sleep, properly fitted.....you can see that there's a ton to get right, or you'll not be treated properly. But if we get all those things in a row, nice 'n tidy, you'll begin to get better rest. Don't be dismayed to find no miracle benefits right away. Your body and brain are somewhat messed up after your history, and it might take a full year before you're comfortable with the setup and beginning to feel right again. Also, don't be disappointed to find that you need monitoring and some adjustment to the settings, usually remotely by a qualified RT (respiratory therapist) for the first few months. As you get better rest, the WAY YOU SLEEP may change, you may lose weight, you may gain weight, you may develop complex apnea and need different treatment....see what I mean? This is a learning AND and adaptive process for the next year, maybe less if you're lucky. Finally, discard a mask that just doesn't work for you after a few tough nights giving it a reasonable effort. Try other masks. Learn what works for you.