This sounds eerily similar to my own situation. For over a decade I've been experiencing exertional/exercise dyspnea (shortness of breath) with concomitant retrosternal chest pain. All manner of stress testing and other diagnostic modalities effectively ruled out cardiovascular and pulmonary causes. So I carried on without definitive diagnosis.
Whatever is going on remains a "mystery". It'd be nice to know how many are in a similar diagnostic limbo. At least it might provide perspective to resolve the issue(s).
Well at least we know we are not alone in this.
