Hi Gabe, is this still an issue for you? I have this exact same problem and at times it gets severe where it causes me anxiety when I can't get that deep satisfying breathe and have to keep trying and trying. I don't have all the answers, but I have noticed that for me it often seems caused by tense/tight muscles and tendons. I have Fibromyalgia, so I am very attuned to my body and notice the slightest aches/pains and soreness that others might not notice. Whenever I get SOB or the inability to get a good satisfying breathe and keep having to try and try to get that breathe, it seems to be related to tightness in my pecs/chest, sternum area, upper back, diaphragm and abdominals. When it's all of these places at once, I am in a bad spot and cannot get a satisfying breathe. There are two tendons in the stomach region that in particular get very tight for me...they are on either side of my belly button and travel from the chest into my pelvic region. It often feels like I am wearing some kind of steel armor that is restricting my breathing when these tendons are tight as well as my pec muscles. It literally feels heavy and tight when I try to breathe. I find that stretching is the only thing that can even get me a tiny bit of relief. I stretch my neck constantly by tilting it in all directions and holding the stretch with my hand on my forehead or back of head. There's also a doorway stretch for the chest that helps. You may find it helpful to look up various stretches for these areas. I think one of the main causes of this is sitting at a computer all day long for days on end as I sometimes find relief when on vacation from work. I also think overdoing exercise can make it worse too, so if my abs are sore...I feel that as a restriction in my breathing. Basically what I'm saying is...there may be nothing wrong with your lungs, nose or anything else, it could be muscle/tendon related. Sometimes after doing stretches I can get that deep breathe. That said...nothing has made this go away and it keeps coming back for me too. It's incredibly frustrating and interrupts my sleep. Right now I'm exhausted from not sleeping well for days. I get up in the night and stretch and sometimes that helps. Anyway...I hope this is helpful info, even if it doesn't fully solve the problem.