Hi Bill
What you have sounds the same as what i have and a number of other people all searching for an answer to what is causing this. Mine developed in January of this year it started off with having difficulty getting a satisfying deep breath and then having this uncontrollable urge to keep yawning in the hope of getting a deep breath. I also have a post nasal drip so i wonder if this could be the cause, but also like you i have a tightness around my rib cage when it is at its worst. I have had this every day since January with not one day passing with it not being there.
I have had so far had endoscopy colonoscopy, chest x rays, ecg, blood tests, and all show nothing, oh and a lung function test which showed normal. I am however going to ent on friday and i hope they are able to find something as i just want an answer to what is causing this.
I hope you also find a cure or a reason to why this has happened, i do take diazepan when it gets really bad just to try and keep me calm and stop the panic setting in as i find it so scary not being able to get a deep breath.
Good Luck