When i lay down and breath in very deeply, i feel a dull pain in the middle of mychest underneath my breast. when i am standing up, i donot feel pain?

R/O PLEURITIS : PLEURITIS=inflammation of the lining of the lung and Pericarditis = inflammation of the lining of the heart can both cause referred shoulder pain. As well as a PE=Lung blood clot. You need a full exam lab testing CXR/EKG/Shoulder X-ray to evaluate your symptoms . Please seek prompt medical attention for diagnosis and treatment options.