Krisy...and other posters who have tagged onto this thread seeking answers. One thing I find that is VERY important is to learn everything you can about SA. Read, Read, Read. Knowledge is power, you will also have better SA communication skills with your medical team.
I agree with Sluna34, I am thinking 5cm's is too low...but then, I am not a doc. Request copies of all your sleep studies...this is not a simple Dr dictation, but a 5 to 7 page summary report for each study. Then as said above, post it in the sleep study forum. This may contain many of your answers.
As for having SA and having Narcolepsy...I have both. Only way to find out is to have a sleep study followed by a 'day' study. The day study is called MSLT...they will have you take 4 to 5 naps two hours apart.
As for still being tired, I am a zombie...but it is not caused by machine..it is other conditions I have. Some of those are aggravated by my machine...but I have to use it. Your fatigue could be caused by many other things with your therapy. DO you have a nasal pillow mask..or nose mask? Maybe you are opening your mouth in your sleep. Maybe you have high leaks, maybe your humidifier is set too high or too low, maybe you have PLMS and that keeps you from hitting the proper stages of sleep...regardless of CPAP. There are several sleep disorders...you may have more than just the sleep breathing disorder of SA.
How has your compliance been? How often do you use your machine?
I'm only a sufferer, not a medical pro. What I post are my thoughts as a sufferer, not that of the ASAA. As a moderator on these forums I oversee the posting rules. This is the internet, always discuss what you read with your medical team.