Google Resmed that might help.

I could not find a cpap mask that would work for me because i am a side stomach sleeper none would seal as they should so i told my doctor i preferred O2 even if it didn't push the air in as a cpap does.

I also have sleep apnea, and on oxygen of a night.

I find i have to keep my bedroom cooler at night seems to make my breathing better. I also use oxygen at night because of sleep apnea, I am not a doctor but you might try some calcium, magnesium, D3 and vitamin K2-MK7 an hour or so before bed time, seems to really help me sleep better and it's really good for the bones. I always get up pretty early in the morning 5:15 am so i am really ready for bedtime to come. I wish you luck hope you find someway to get restful sleep at night.

I have trouble falling asleep I'm up until around 3or4am almost every night....seems like my breathing is heavier at night