I am a 20 year old college student studying in Kolkata. My lifestyle is very active and have to travel around the city quite often. I have to use public transportation and myself to travel from here to there. My problem is my weight and my decreasing appetite. I am underweight and I am having difficulty in gaining weight due to lack of guidance in what to eat. I can't have heavy food or a large quantity of meal because every time I do that I have to take a dump soon after. I feces are okay and I don't see any problem, but my problematic stomach and weight is causing me a lot of problems. Please help and suggest on what I should do ?