Pain that worsens on deep breathing and sits around the shoulder blade is usually musculoskeletal - costochondritis or a strained muscle from posture and long desk hours - not the heart, because cardiac pain does not change with breathing. But at 50 I would not close the file on that alone: one ECG is worth doing, plus BP,
sugar and lipids if not checked recently. Meanwhile hot fomentation, avoid heavy lifting, correct your sitting posture, paracetamol for the pain. Straight to the ER if the pain becomes heavy and central, spreads to the jaw or left arm, or comes with sweating or breathlessness.
Next Steps
Get an ECG done today itself for peace of mind. Send me the ECG on a Practo consult and I will confirm whether this is just muscular or needs a cardiac work-up.