My doctor wanted me to get a mouth and nose mask. My CPAP technician convinced me just to get a nose mask. He said everyone thinks they need to breathe out of their mouth, but he suggested I would quickly get used to sleeping with my mouth shut. I was doubtful, but he was right. What you're doing is very beneficial. The only thing you're not getting, I guess, is the air being forced into your nostrils. You might not need that anyway.