Fell 6 days ago. Next day my right side chest hurts and difficulty breathing. Dr says pluerisy. How can he diagnose without tests?

Pleurisy. Pleurisy is a clinical diagnosis meaning it is based on your history and a physical exam. It is also possible you could have a rib fracture or a bruising or strain of an intercostal muscle (muscles between the ribs) but these are not treated with anything beyond pain medication as is the case with pleurisy.