As gluten's in all grass-grain (wheat, barley, rye, etc) products, symptoms should be worse when you consume them. Oatmeal's an oat. If you eat bread or bread products, and have stomach pains, trouble digesting, anemia, or other stuff (a complete list is available online, but I wouldn't trust the Internet to be a medical professional), it's something to consider. I wouldn't trust the internet to diagnose anything.
Oatmeal shouldn't have gluten in it, as it's an oat.
Random people on the interwebs aren't a good substitute for a qualified medical professional. See your doctor, but as doesn't sound painful I wouldn't freak too much.
Hope this was at all helpful.