Hi i have had throbbing pain under my left shoulder blade for 3 weeks. when i sneeze or cough sit or lie down it hurts. i am in an office job. is this?

Likely Muscular Pain: If there are no other symptoms like shortness of breath or feeling unwell, it might be due to pain of the muscles. It might be due to your posture when sitting in your office. Simple pain killers is useful to help with breathing and changing position, and physiotherapy might help. If symptoms persists though you might need to see your doctor for further assessment looking for other causes

Many possible causes: There are many possible causes. As Dr Al Shaar mentioned it could be from your muscles. As you have a cough and it hurts when you cough and sneeze it may be pleurisy = inflammation of the covering of your lung from a mild lung infection. It would be a good idea to have an online consultation to clarify better what you are experiencing.

Need evaluation: This could be musculoskeletal, pulmonary, cardiac, diaphragmatic, and needs and an evaluation. Your physician will need to do imaging, to help you clarify your symptoms.