I have the same issue, in one end and out the other and couldn’t go out for 5 years and no quality of life. What has made life possible is KELP. I take kelp once a day and it has helped me so much. I still have to be careful with what I eat……I’m not gluten intolerant but am careful with that. I think you should give it a go or go to a naturopath. There are experiments in giving cattle Kelp to lower methane and as flatulence comes with my diarrhoea I thought I would try it. Your stomach can be over or under acidic and kelp keeps it neutral I think. All I know is that it has me 80% better…..Not a medical professional. IBS is a title for the fact doctors don’t know! Try a good quality Kelp and good luck.