Hello @barbflynn, Welcome to Connect. I can tell you from my experience that you are not doing anything wrong. It is a learning experience when you first start using a CPAP machine. When I first started using a CPAP a few years ago, I also experienced my mouth filling up with air. Sometimes so bad that I ripped off my mask in the middle of the night. I found out by trial and error that the air pressure was a little too high and was able to lower the pressure some which helped. My CPAP machine had a ramp-up feature that started the pressure at a lower level and then it gradually built up as needed. I was able to tap the ramp up button on the CPAP machine as needed when my mouth filled up and it would help with the air filling up my mouth.

If you haven't already discussed the problem with your sleep medicine doctor or care team, I would recommend calling them as soon as possible. Here is more information on your question that may explain why it's happening and possible solutions.

--- Swallowing Air with CPAP (Aerophagia): Causes and Solutions:
https://www.cpap.com/blog/swallowing-air-with-cpap-aerophagia/
--- Troubleshooting Guide for CPAP Problems:
https://www.sleepapnea.org/cpap/troubleshooting-cpap-problems/.
I am currently using a ResMed AirFit F20 full face mask along with a CPAP mask comfort cover recommended by my sleep medicine PA (https://cpapcomfortcover.com/). I do get a little air leak with the comfort cover but I am still able to keep my AHI events to my target number below 4 per hour. Finding a mask that is comfortable and works for you is key to helping you continue to use your CPAP machine.

While we wait for fellow CPAP members to share their experience, can you share which type of CPAP mask and machine you use?