This sounds so much like me. Took 8 years of ER visits, living off Imodium and B12 deficient. I went gastro to gastro demanding another endoscopy. Was told no, I had one already in less than ten years, mine was a little more than a year, but I knew something was wrong.
I finally found a gastro who actually got it and did it for me. Found so much more than the last one did. Have them look for pernicious anemia in blood labs. They found AMAG during my endoscopy, they did a colonoscopy as well. Thank GOD someone looked and found it. They were shocked. My suggestion is, make them do it. If they refuse, find another. I was told I was crazy by so many. Well who is crazy now! Listen to your body and be your own advocate. By the way, I waited two years for my docs to get me into Mayo. I called once a month and pleaded my own case and I got myself in after my test showed what they did. Never give up and fight for yourself.
Make sure to have your labs for pernicious anemia. Fight for the colonoscopy/ endoscopy or the smart pill! Best of luck to you!!!