severe chest and back pain [anxiety attacks]

My boyfriend has been complaining about a chest and back pain on his right side for about a week now. It came totally out of the blue. Its causing him to have constant anxiety attacks, nausea,  no appetite, shakes, and he has trouble breathing at times. He says he feels like hes dying. Tuesday night he was brought to the emergency room, where he had an EKG. Everything should up fine, so the doctor put him on .25mg of clonazepam for the panic attacks. He's been taking it for the past few days, and the panic attacks have calmed down, but the back and chest pain hasn't. Not only is he but I am scared for him. I don't know what to do to help him.  He doesn't know what the pain is being cause from. It seems like there's a huge knot in his back. I constantly work at the knot to see if the pain will go away. It does for a short amount of time, but then the pain is back again.