Nowdays even younger people have problem of constipation, if your diet include only junk foods and fast foods and mainly non vegetarian diet without balancing it with food items rich in fibres this problem will arise. And taking food on untimely hours or skipping it because of your busy work life will lead to gastritis which might be the reason you are feeling fullness or gas. I suggest you to plan a proper diet which includes atleast 35 to 40% of vegetables and it should be rich in fibre content if u obseve the diet of westerns even though they mainly depend on meat, they make it a point to include vegetables in the form of salads and do yoga and meditation which will help you to destress.