You are right. I sleep on the sides but with pillows, and suspect I am a mouth breather too. But if you don't use the pillows, the mouth does naturally remain c

You are right. I sleep on the sides but with pillows, and suspect I am a mouth breather too. But if you don't use the pillows, the mouth does naturally remain closed. However, I am still sceptical about this as without the pillow to support the head / neck, I think breathing is bit more laboured. Moreover, in my experience, sleeping on the side puts a lot of pressure on your neck and shoulders and you often wake up with sore muscles in those parts of the body.