Hi - Make sure they ruled out celiac for you, if they did you don't need to go gluten free for IBS.
The insoluble fiber in brown rice can set off IBS - white rice is safest. Usually brown rice is a pretty tolerable whole grain, along with instant oatmeal, quinoa, polenta.
I would take the whole grains out until you are stable, stick to the white rice, rice noodles, peeled cooked root veggies, bananas, etc. from the safe soluble fiber list https://www.helpforibs.com/diet/fiber1.asp
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