Are you a mouthbreather?

So at my most recent visit to my dentist, I was asked if I was a mouthbreather. This would supply the answer as to why my gums bleed when flossed, even though I floss daily. I figure I am a mouthbreather, cause I breathe through my mouth, (duh) but especially while asleep, and the dentist told me that means my gums and mouth flesh in general would be dried out, thus, bleeding gums. Do you have the same problem? Should I bother to do anything about this? What can I do?