Stilltired

I was diagnosed with Sleep Apnea 10 years ago. I have always gone though periods of time when I have headaches all day long after coming off of my C-Pap. I recently had a new sleep study and got a new C-Pap machine. I feel sometimes while sleeping I do not feel the air coming into my nose but I still manage to fall asleep. Often waking up still tired the next day. I just noticed after waking up from a nap that I could barely feel air pressure going in my nose. I am experimenting laying different ways hoping to find the best position for me at this time. Positions that were fine before are not working now. I was thinking maybe its something in my sinuses that are closing up and not intaking the air. Any suggestions or has anyone experienced this?