I had about 5 feet of my ileum removed along with the ileocecal valve and part of my cecum due to a cecal volvulus. I was put on Immodium for many months post-op to control the diarrhea, but perhaps this is not advisable for you due to your narrow intestines. I was recommended a book called "A Patient's Guide to Managing a Short Bowel" by Carol Rees Parrish. It is free to patients and was a great guide. Prior to my volvulus/emergency surgery, I struggled with constipation issues, so my picutre is quite different from yours, but since my journey began I have been treated for SIBO four times. Three times I was put on Xifaxin, this last time I tried an herbal antibiotic combination. SIBO symptoms can be pretty intense, so along with treatment you can try a low FODMAP diet to help things calm down. One of the most helpful things I did was to connect with a RD who specialized in GI issues. Mine is out in CA (I live in WI) but we conducted our sessions via Zoom. I was able to expand my diet and understand what foods would work best for my unique set of challenges. I pray that your new GI doctor is helpful and for relief; I know that feeling a hopelessness!