What Causes Severe Pain In Shoulder?
tricky; cannot say in your particular case
Detailed Answer:
without examining you. BUT in general the location of the pain and what causes it to hurt are clues to what is going on. While it is possible for heart condition to give pain over a broad area, and give shortness of breath, if the pain is sharp, short and triggered by breathing, as if it is a sore spot being poked.... the deep breathing is not poking the heart but may be poking the lungs, diaphram, or even the liver.
Pneumonia or other less serious infections or inflammations of the lungs can give pain that is triggered by deep breathing and, this pain usually radiates out to the shoulderblades, the back, sometimes lower neck. a blood clot to the lung could do it also, asthma with overinflation and strain on the lung. Less likely .. but still pretty common, irritation of the area where the stomach and esophagus rub onto the diaphram can be irritated iwth a hiatal hernia. Deep breathing triggers pain. But it is more often central or right sided.
without directly seening/examining and asking direct questions in person I can only give general information on what is likely to be occurring.