Pain In My Left Breast When I Breathe?

Pleurisy.As a result of this illness, you will feel stabbing pain beneath your breast, which will become worse if you breathe deeply.Pleurisy is a painful disorder that affects the muscles under your breast.Pleurisy is caused by inflammation of the pleura, which are the thin membranes that wrap the exterior of your lungs and the inside of your chest cavity.Pleurisy is a contagious disease that affects the respiratory system.