I agree with Kitty. I do however recommend taking a cardiac stress test. Another thing it could be is Esophageal Spasms. I don't think so because of the constant pain but just thought I would mention it just in case. If it's chest wall spasms like your doctor says see if ibuprofen helps relieve the pain.
Good Luck
Johnnie D. Jackow Sr - Total Body Fitness
Fitness Expert/Author