Possible to get stomach discomfort because of meditation?
Possible Causes:


You are eating too much and too soon to doing sitting meditation. While meditating or doing any relaxing activity, your digestive system functions much better thus producing more gas along with other things. Solutions: eat less and have at least an hour or two gap for meditation or try a different posture like standing/non-lotus.
You are stresing out (more than normal) while you are trying to relax (meditate) thus causing intenstinal ineffectiveness. Let go of those thinkings and be present and pleasant.
You are already quite gassy. Have some probiotics in the form of yogurt, kombucha, or fermented food.