I know a lot of people have already commented on this but I thought id just add my two cents. I dont have a lot of time so I have to make this short but trust me when I say youre not alone. I went through this for six months and nobody believed me, even my fiance thought I was making it up. I feel like telling you this part might make you worry but in my situation I have a very old furnace and it was drying my throat and nostrils out to the point that it made it hard to breathe. Turns out I had severe allergic rhinitis. I wont go into details because its a lot scarier than it sounds but long story short they gave me a shot and some nasal spray and it went away. I ended up being so scared of it coming back that I started doing the same thing you are now. Am I breathing correctly? Omg im dying. Illuminati. Anyways the best part about it is I also lead up to that, I had health anxiety about everything and once I got over a particular body part or bodily function it upgraded to a more important one. Eventually I found my way up to breathing, which is in my opinion the scariest health anxiety to have because you constantly feel. Anyways back to the best part about it, once you overcome this you can actually relax, I mean youve already survived cancer and heart disease and lung failure so really what else is there you know? Ended up being longer than I thought and my fiance is like missah lets go because thats what she calls me, I know its weird, but I just wanted you to know theres definately a light at the end of the tunnel, and once you can finally bathe in it it feels amazing. Youll get through this, just remember how strong your mind really is and that if you dont control it than it will control you. Good luck.