some of us have very "stuffy noses". I frequently get blocked nasal passages, and only by religiously using a steroidal nasal spray can I breath through my nose. I've had to travel to another city just to get my nasal spray on two occasions, when there is literally zero stock in my city (just prior to hay fever season), so access to this is not a given.
Obviously yes, mouth breathing sucks for a variety of reasons, but if you can't breath through your nose it is significantly preferable to the alternative.
It's a self reinforcing cycle, the more you breath through your mouth the harder it is to go back to normal breathing.
It's like saying being fat makes it hard to exercise so you don't exercise, which makes you more prone to stay fat, which makes it harder to exercise, &c.
It's unlikely you wouldn't have noticed this if it were the case but my nose tends to block too by some reason if I lay on my back. What I observed though is that if I lay on a side, there's some mysterious movement about where the sinuses are and one nostril gets unblocked, I think the one facing up (not touching the pillow). If I switch sides, the blocked and unblocked nostrils switch places. So oftentimes I breathe though just one nostril but still beats breathing through the mouth.
"Stuffy nose" tends to go away too once you start breathing through it all the time. This, of course, doesn't apply if you have allergies or are sick with a cold or something - those are legit reasons to have a "stuffy nose".
No, not true. I exclusively breathe through my nose all day (unless panting from a workout). The moment I lay down, something changes and my nose stuffs up. This has only gotten worse over time. If I were to, say, tape my mouth shut, I would absolutely suffocate in short order.
You might want to really clean your bed (pillow, sheets etc) and surroundings from potential allergens like dust mites, mold, pollen etc. Ideally with one of these mattress vacuum cleaners. Window sills (even outside, if the window doesn’t seal hermetically) might leak mold spores or other particles into your bedroom. A really good air filter next to the bed might also help.
>>"something changes"
When you lay down, blood shifts to your head which can cause your nasal passages to become engorged with blood, causing a stuffy sensation.
Obviously yes, mouth breathing sucks for a variety of reasons, but if you can't breath through your nose it is significantly preferable to the alternative.