Microscopic colitis is split into lymphocytic and collagenous (a layer of collagen that shouldn't be there). I make GF sourdough bread because wheat sourdough still has more than 20 ppm gluten (the limit for GF). Gluten from wheat, rye, and barley is in a lot of things. Unless they are labeled GF, soy sauce, malt, a lot of processed foods, and risk of cross contamination if a, for example GF pizza is cut on the same surface as a regular pizza. GF is equal to a tiny crumb of wheat/rye/barley flour. When I went GF 15 years ago due to celiac, my acid reflux, skin rashes, GI problems, and others disappeared (unless I get glutened). You might consider keeping a food log because when I got collagenous colitis 8 years ago I figured out I'm also sensitive to legumes, NSAIDs, and dairy. I am not allergic to wheat or dairy, but they still trigger my immune system.

There is info on collagenous IBD and other diseases in ResearchGate. Here are links: https://www.niddk.nih.gov/health-information/digestive-diseases/microscopic-colitis/definition-facts#:~:text=Microscopic%20colitis%20is%20a%20chronic,inflammatory%20bowel%20disease%20(IBD). https://pubmed.ncbi.nlm.nih.gov/24440672/#:~:text=Conclusions%3A%20Oral%20budesonide%20(9%20mg,ClinicalTrials.gov%20number%2C%20NCT00450086.