'Forgetting' to Breath?

I'm a 43 y.o. 'intermitent' smoker who has had some breathing problems in the past (e.g. EIA, when I used to run track; allergies manifested through coughing in the summer/spring months, etc.)  None of this has been debilitating at all and in fact have only just this year started taking something for it (Singulair, 1x/day).  However, during the past year I have been having a different problem which is difficult to describe. I did read a previous post that describes the prob. to a "t."  If I may quote:  "I have a "heaviness" in my breathing.  As I reach the end of an exhale, it is though my lungs wish to keep moving in that direction--as opposed to reversing the process  and inhaling."  I have been to the emergency room 3x for the past 4 months with this feeling.  I had a normal PFT, normal chest x-rays, and 100% pulseox reading.  I have no cough and rarely have shortness of breath. It's almost as if (as one doctor put it) my lungs/chest "forget" to breath.  I am not ready to attribute these episodes to panic (I have experienced panic attacks in the past), as it doesn't 'feel' like a panic attack, and the problem also surfaces after I have taken an ativan (I'm very sensitive to the ativan and it only takes .25 mg to get my attacks under control.)  I'm not even convinced it's a lung problem...could it be muscle-centric instead?  I hope you can give me some advice; my internist is a great guy, but I think he is beginning to think this is 'all in my head' and I'm truly not convinced of this (yet!)  This is severely curtailing my lifestyle and any advice you can give is welcome.

[National Jewish]

Since your PFTs, chest x-ray, and oximetry are all normal this is not a lung problem.  What you have described strongly suggests a panic disorder.

My advice would be to take the Ativan