tJanet, This is miserable for you. I have a bit too long and severely damaged in my small intestines , I have been way too long, redundant splenic(splenic just means it is on mu left/descending side of large intestine. I'm get more baffled (my word for angry at drs) when they can't or won't help. The intestinal tract, from where the food goes in to where the food comes out, is the simplest definition of a GI Dr. That I know of. But I'm in no way surprised by your inept response. I am not much help with diarrhea, cuz the multitude of times I have it, I have caused it on purpose to deal with CIC(chronic idiopathic constipation).
Besides doing nothing and stay in pain, getting a new GI; you might try a colorectal specialist. I did not know what this is, someone said maybe I should look into at least a phone/video consultation with this type of doctor. It seems like, they would be like a GI-intestinal only specialist. I found the term under cancer. But, they treat non-cancer patients too. Hopefully you have insurance that covers a referral of this kind.
I suppose, you didn't have your small intestines mostly removed, for fun. So, how you treat the diarrhea and what is causing it might make a difference in how you treat your diarrhea. If you're not on any dietary restrictions, have you tried all the more constipating foods? For me, fiber is a double edged sword. Can you increase your fiber intake, via fiber supplement?
My new 1st, 2nd, 3 rd opinion options are: AI's. I don't even know how I found this. I'm sure you already know this, I didn't. I finally got the app, free, for POE. Inside it has many many options. Examples: Tarot Reading, mental health, physical health, how to peel a mango 😛, I love mangoes but they are buggers to peel.
I have several issues that I am getting zero help from the doctors, so I posed a very simple question, like is measles's or Rubella (German measles) worse? I knew the answer, but I used it to see how AI/POE work. I found that the more detailed explanation I give, even if it is long winded, the better results I get. You might give it a try. I would offer to trade you, some of your diarrhea for some of my CIC, if it was possible. Good luck!! Shelley

tJanet, me again, I just saw on the right side of my screen a blog for GI plus issues. I have not used any of the blogs, but, hey, they are the ones suffering and might have some good ideas for you.