"A Simple Routine Condition failed to be diagnosed"

During May I was taken to A & E at Peterborough City Hospital by ambulance with acute stomach pains. A few hours later i was discharged with an incorrect diagnosis. Pains persisted, but not as acute and medication was taken as exactly as prescribed through June/July. I was later readmitted to A& E with the more significant acute acute pains. Discharged a few hours later. After Discharge saw my GP who arranged for tests at a local clinic, immediate diagnosis of gallstones - Simple !! Why was I subjected to months of unnecessary pain and worry, when this should have been a simple routine matter to diagnose? Why were Peterborough City Hospital incapable of diagnosing such a routine condition? How much extra cost has the taxpayer had to fund as a result of the inability of this hospital to make a simple diagnosis? Very Poor - I now have virtually no confidence in this NHS Foundation Trust