CPAP and OLP etc.

I've been using a CPAP for about a year and a half and suddenly I'm waking up with such dry mouth I know there has to be something wrong and I suspect I'm mouth breathing during the night. (I go thru almost a tank of water every night.)
My concern however is my teeth and oral mucous membranes. When I wake up in the middle of the night, I'm so parched and my mouth so dry, I almost can't even open my mouth enough to take a drink of water.

I have oral lichen planus. Anybody else who has any kind of disease of the mouth who also uses a CPAP I'd love to hear your thoughts.

I don't take any medication that would dry me out however I do have an oxygen concentrator in the room which heats the room up like crazy. But this is new. It causes me to only use it 4 hours a night now. Anyone else have issues with your mouth that could be impacted by CPAP and what actions helped? I can't use a full mask and I don't know if I could do a chin strap. Thanks.