Something similar happened to me. I discovered that I was lactose intolerant. I have been through a long route including the FODMAP diet and later limiting fermented foods, along with not eating wheat products. Gastro doc did two colonoscopies, no red flags. I finally used a nutritionist and had the SIBO test done. We got some things sorted out and I am feeling better. Still am not sure what causes what. It is a long, snakey trail for most of us. Hang on and use your common sense, you will find some solutions.