I coughed hard and immediately had a sudden sharp pain behind my right shoulder blade and it persists when take deep breath, now feelshortness breath?

Varies: There are a lot of possibilities and i would encourage you to get checked. Many potential causes are musculoskeletal and quite benign, such as a subscapular bursitis or a thoracic radiculopathy. But there are more potentially dangerous conditions including the possibility it is an abnormal presentation of cardiac ischemia. A detailed exam and appropriate tests can usually determine the cause.