This might be ridiculous, but maybe try this:
Sitting in your chair, at home, just as comfortable as possible: Breath through your nose, and then stop it.
Can you do that? If so, start experimenting with how you are stopping/starting your ability to breath through your nose until you have a strong sense of what is going on and can control it in a comfortable setting.
The idea is that, if this is mental, then you are doing something. If you can learn to do it on demand, you can then learn to feel what is happening and control it better.
It is a bit like wiggling your ears. Everyone has the muscles to do it, but almost nobody has the muscle control to do it, but you can teach it to yourself.
Anyway, it is just an idea. Hope it helps.
Sitting in your chair, at home, just as comfortable as possible: Breath through your nose, and then stop it.
Can you do that? If so, start experimenting with how you are stopping/starting your ability to breath through your nose until you have a strong sense of what is going on and can control it in a comfortable setting.
The idea is that, if this is mental, then you are doing something. If you can learn to do it on demand, you can then learn to feel what is happening and control it better.
It is a bit like wiggling your ears. Everyone has the muscles to do it, but almost nobody has the muscle control to do it, but you can teach it to yourself.
Anyway, it is just an idea. Hope it helps.