Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.

Sorry you're having some troubles and hope the figure it out. Hard to know what's what, is it lungs, is it heart, etc. I do wonder though if you've been checked for anemia? When I'm anemic, usually around my period, but I have problems with anemia generally, I feel short of breath. Just a thought.