About a month and a half ago I starting have a deep pain in my back. It would hurt slightly when I took a breath. It continued to get worse especially when I arise in the morning after a night of sleeping. When I get up it hurts to move, breathe, and if I try to lay back down the pain get so bad that it radiates to my left arm...so I have to sit up. After about a half hour or so of moving about the pain lessens. Now the pain is lasting longer during the day and going into the middle of my chest and then it subsides again until I go to sleep and then in the morning it starts all over again? What could be the cause? I have not injured myself. I've been to the doctor and I've had an x-ray of my back and it was clear...my lungs upon listening to them are clear also? It doesn't hurt to lift anything or bend over? Not sure what is going on?