About 2 months ago, I was trying to restrain my large dog from making a break for the door. He jerked my arm, hard, backwards. Since then, I have had pain in my rt. upper arm, which has been progressively getting worse. It hurts when I lift my arm to the side, up to brush my hair, or rotate it backwards. It is weak and hurts when pressing on the area where the deltoid attaches to the humerous. It aches constantly at night. Can anyone give me any ideas what this might be?