Having pain & numbness in mid back-up shoulder, and isnt going away, should i be concerned? what could it be caused from? what can i do to relieve it?

This depends on the : Length & severity of symptoms with potential causes being localized to a lower cervical neck issue like a disc herniation to a nerve entrapment about the shoulder or a shouldef condition . There is a nerve called the long thoracic nerve that sometimes may cause these symptoms. Treatment is dependent on the cause so see a physician if symptoms bothersome and persisting or progressing.