I've never had a problem with porridge - I make mine with soya milk. I find rice milk too "thin" and doesn't keep hunger off for long enough!
Presume you didn't wash it down with coffee ?!
If you feel it's definitely bothering you, you could experiment with gluten free oats or millet flakes instead.
New stuff: GERD. Interstitial Cystitis
Lifelong stuff: Food allergies, eczema, asthma