Thanks for that. Sadly, I'm far more likely to get useful information from the Internet than I am from my medical team. I actually turned to YouTube to "fill in" details the technician didn't bother to tell me- namely that "mask leak" with a nasal pillow can be caused by opening your mouth. I also was able to work out, thanks to videos, that the nasal pillow I was told to use was a terrible fit for me, which is why I felt like I was suffocating and unable to breathe the first night, but the correct size was thankfully in the box. It's been much smoother sailing since I swapped to the correct size pillow.