Did the ER scan your gall bladder and abdomen with ultrasound? Gall bladder pain can radiate to the shoulder - if it's not been done your primary carer can arrange it for you with liver function tests (a blood test that also shows if any element of jaundice due to gall stones etc).
At this stage it's a question of keeping on knocking on doors until you get answers, and a GI consultant would be a good place to start.
New stuff: GERD, Recurrent cystitis/Overactive bladder
Lifelong stuff: Food allergies/intolerance, eczema, asthma