I am recovering from a stage 2 shoulder separation that occurred a week ago. pain in pectoral adjacent to injured shoulder when breathing deeply.

Chest pain: When it comes to chest pain, we ask a lot of questions to start with. Available info here is not enough to make any approximate diagnosis but what goes against cardiac type of chest pain is the worsening element with deep breathing. This is usually more indicative of musculoskeletal pain and atelectasis (collapsing lung tissue due to insufficient breathing usually)... consider talking to a doc.