It is clear from your description that your overriding symptom is pain, not shortness of breath, and that the pain
increases with deep
breaths and acts as a deterrent to taking deep
breaths, sensed as shortness of breath.
Much chest pain, especially in young athletes, is: 1) of musculoskeletal origin, such as fractured ribs or sternum, torn cartilage, torn or badly stretched intercostal ligaments; or 2) the result of blunt chest trauma, often seemingly not serious at the time of occurrence.