hi Tamra,
It's easier to read posts when they are typed in small letters, not all capital letters. Typing in all big letters looks like yelling. But, hey, sometimes the aggravation of this kind of therapy makes us all feel like yelling.
I agree with the others who've said, check to see if your humidifier is working. Also, some heated humidifiers seem to simply produce more humidification than others. Even so, when I use my full face mask (ResMed Ultra Mirage FF) for mouth breathing when my nose is congested, my mouth does get dry no matter what. Even with humidifier turned up to the highest heat setting, and even with the Australian heated hose to control rainout, my mouth will
still get dry. The constant rapid flow of air through an open mouth simply
will do that. Just another of the minor downsides I put up with to get the fabulous upside of better sleep even on nights when I cannot breathe through my nose.
Tamra, if you are normally able to breathe through your nose fine and are using a FF mask only because your mouth drops open at night (not because you
need to breathe through your mouth) you might want to look into some other methods of keeping your lips closed so you can breathe through your nose. Chin-Up strips work for some, chin straps (especially soft, homemade ones), taping the lips closed.... there are lots of things to try. It may be, though, that even if you breathe through your nose fine while sitting up, you get a stuffy nose after you've been lying down awhile and need to keep using the FF mask. As snuffle-nose pointed out, it wouldn't be a bad idea to have an ENT check your nasal passages, especially when you are lying down.