Hello,you change your diet habbit ,Start having more protein containing food. Too much of carbohydrates are not good for health ..Medicines have side effects and withdrawal effects .. Doctors usually don't prescribe medicines for weight gain.
High-protein foods include meats, fish, eggs, many dairy products, legumes, nuts and others. Eat plenty of high-carbohydrate and high-fat foods if weight gain is a priority for you. Go to a gym and lift, 2-4 times per week. Lift heavy, and try to increase the weights . Working in gym helps to increase appetite