Oat groats vs. oatmeal

A few years ago i started eating oatmeal (Quaker rolled oats), and i used to get acid indigestion every time, even after a small amount. I haven't had oatmeal since then. Then a few days ago i bought a bag of oat groats, and i had them this morning. No indigestion at all! I decided to try oat groats because i was reading a book, and it said you should buy the whole grains and prepare them yourself, so it's fresh. In prepared products from the store (flour, oatmeal, bread, etc.) the nutrients start oxidizing shortly after it's made.