You are young and may be working female. Stomach issues start when one does not take care of the food with respect to timing and quality of food. Eating at irregular time and eating out is the main culprit. Also you should be sleeping on time as lack of sleep also weakens the digestive system
Next Steps
Stop eating outside food completely and give up dairy products like milk and bread. Have water around 2.5 liters daily
Health Tips
To have breakfast at 0730-0800, lunch around 1230-1300 mid evening snacks at 1630-1700 and dinner always before 1930-2000. Give up oily and fried foods.
All above are conservative methods and will definitely help and if not needs to be investigated