Hi there....first and foremost you will need to get your haemoglobin and
sugar levels checked first to find the reason for weakness. Anaemia is a very common disease among Indian women, which can cause weakness. Also regarding gaining weight, it is a very gradual process. It will require strong determination and patience. You will have to follow a healthy diet and do regular excercises. From diet point of view, you need to start having lots of protein rich foods like pulses, boiled egg white, boiled chicken, vegetables and fruits. From excercises point of view, start slowly with brisk walking, then change over to cycling or swimming or even aerobic excercises. This will help you build muscle mass. You can consult a dietician who will draw up a diet chart for you. And general physician for the blood tests