Jaw pain from CPAP. Possibly not lining mouth up correctly?

Hi everyone. I just left a message on my doctor's voicemail about this, but I figured it couldn't hurt to get opinions here while I wait to hear back.

I've been using a CPAP machine (with an ESON nose mask) for about a week. For the past few nights, I've been waking up with pain in my jaw. I've tried googling it (which is how I found these forums) and it seems like the most common cause of this is clenching your jaw in your sleep. I don't think that's it, though. It feels more like my lower jaw is misaligned with the rest of my mouth.

I've tried switching to a thinner pillow, but that didn't make a difference. I've always slept on my side, but before the CPAP machine I tended to have my face more in the pillow, not quite sleeping on my stomach but almost. I've also noticed that I keep waking up with my arm asleep, so maybe I'm sleeping in an awkward position? I used to mouth-breathe, although I haven't had any problems keeping my mouth closed since I started CPAP. Could that have anything to do with it?

Any advice on how to fix this would be appreciated. Thanks.

Could you be clinching your jaws tight in an attempt to prevent air leaking out of your mouth? If so, that could account for the jaw pain.

I don't think so. I've been surprised at how easy it's been to sleep with my mouth closed, actually. I might try picking up an over-the-counter mouth guard just to see if it makes a difference, though.

Is it you upper jaw or both?

For me couple times I had problems with jaw pain it was because of the size of the full face mask. I was using the Airfit F20. Bottom portion of the medium size cushion would come close to pressing my lips (and consequently lower jaw) so switching to large size resolved this as the bottom of the cushion/headgear would seat farther down on the face towards chin. I had exact same experience with AirTouch medium size cushion and solution again was to use a large size. Each time it took 2-3 days before I could experience the pain and then another day or two after switching to the large sized mask for the pain to abate.

I would have to guess nasal mask does have similar effect on the upper jaw but I couldn't be sure.

Just the lower jaw, and just on the right side. I usually sleep on my right side, so I'll try sleeping on my left tonight.