I've had IBS for something like 23 years. I assumed it's something I'll just have to live with the rest of my life, until recently I came across the work of Dr. Mark Pimental. Dr. Pimentel has devoted his life's work to attempt to defeat IBS, and he has come up with some interesting discoveries.
I would strongly urge you to read this article here:
https://chriskresser.com/a-new-understanding-of-sibo-and-ibs-with-mark-pimentel/
Basically he says that IBS is caused by SIBO. SIBO is caused by a case of food poisoning.
There is a blood test that can determine whether you actually have IBS with 98% certainty. It's a blood test for the biomarkers anti-cdtB and anti-vinculun. Your gastroenterologist likely has never heard of these markers, but if you push hard enough you should be able to get them to run this test for you. In addition, you need to take a SIBO breath test. The blood and the breath test complement one another and are how you determine your treatment plan. The information dictating the treatment plan can be found in the link above. You should strongly urge your doctor to read that article as well.
Search Youtube, there are quite a few videos of Dr. Pimentel discussing different aspects of IBS. I recently learned that I was triggering IBS events every day because I was using artificial sweeteners like stevia. There is tons of good information in these videos...
https://www.youtube.com/watch?v=vrJbsfAe0xI
https://www.youtube.com/watch?v=p315cSqTfEM
https://www.youtube.com/watch?v=Ean8Rc0AKTM
There are plenty more.
Hope this gives you a good start in the right direction. Good luck.