This feeling of gas in the sromach or some other place in the body is mainly because of some sort of discomfort. Some time in indigestion
or some specific food item lead to excessive gas formation and we are not able to expel that out which produces a sense of uncomfortable feeling.
This can be controlled by avoiding the food artical which causes this type of feeling or you can improve the method of eating also which can also improve this condition. Try to eat in a way to decrease air intake with your food. This traping of air with food also some time can lead to this thing.
Apart from this some time acidity or formation of ulcer can also lead to this type of feeling . So i would suggest you to take some over the counter anta acids and see if this is relieved or not.
Thanks and take care.