Thanks for writing to the forum!
It is slightly unusual to experience pain in that area. This could be due to stomach (as in acidity, GERD), pancreas (pancreatitis), spleen (abscess or lump or enlarged spleen) or heart (heart attack). Pin getting referred to shoulder should be investigated for heart pathology. Also a pain radiating to the back could be due to pancreatitis. It could also be a pain of costochondritis.
You will need to undergo CT scan, EKG, blood tests etc. to reach a diagnosis. It is difficult to comment beyond this at this stage. Lets see what your doctor says. Please let me know if there is any thing else and do keep me posted. Take care!