What Causes Chest Pain Radiating Towards Sternum And Back?

For a week, I have been experiencing severe chest pain which wraps thru my sternum to my back. It is a gripping awful sensation. I went to the ER on Saturday and an EKG, chest xray, and cardiac enzymes were all WNL. I am still in agony. I ve used a heating pad, taken Motrin, even Nexium as I thought it could be esophageal spasms. I have been a RN for 20. I am a white, 40 year old female.