Hi, You are very young. Why you want to harm your body ?Steroid and  weight gain capsule have adverse affect on body. Don't go on advertisement they never tell any side effect.  You can go for better and healthy option. See, There are many reason of being underweight. 1. Endocrine disturbances 2. Genetic 3. Vitamins and minerals deficiency 4. Psychological problem 5.IBS 6. Eating disorder 7. Liver dysfunction And many more   So my opinion is to contact directly to us so that we can find the cause and suggest according ly.