I had heart cath last july and it was fine. i still get pain in mid back, sides and chest. i take protonix (pantoprazole). if not heart or gerd could it be stress? if not that then what?

See a doctor: Yes, this could be stress, along with a dozen or more other things. You need to be seen by a good clinician who will spend the time and effort working this out with you. Good luck.

Pain: There are multiple reasons for your pain and you have either ruled out or are treating two of the most concerning. Another cause of pain you are describing is musculoskeletal, so follow with your primary physician for further evaluation.