A lot of the gas in your stomach is from swallowing air, and when you eat you naturally swallow small amounts of air. If you drink a lot of carbonated drinks, through a straw, chew a lot of gum, or eat too quickly, then you could be swallowing more air than usual. You keep farting as a way of releasing this excessive gas building up. Although this particular kind of gas usually comes out through burping, some might end up coming out the other way because there’s too much.