I have been having upper back pain that radiates to the chest and i mistake it for chest pain. it's worse if i take a deep breath. my chest x-ray was normal. what could this be?

Possibly serious: It is possible that this pain could be serious. The most concerning possibility would be a blood clot in your lung. This would cause a feeling of shortness of breath. This is often not seen on a plain chest xray. You would need to go to the emergency room to be seen for this. The other likely less serious cause is a muscle pull. This would cause more pain with movement without a deep breath.

Pleurisy: It could be combination of things it could be a pleurisy which is an inflammation in the pleura or could be inflammation in the cartilage part of the ribs or could be a referral pain from deep inside like pancreas gallbladder or an ulcer all can cause similar pain with normal chest X ray your doctor should referred you to the appropriate specialist