As you suffered from MDR-TB for a very long time, it might take more time for you to gain weight. But it is very essential that you have a nutritious, high protein and right fat diet, in regular food intake you may start including at least one litre of milk, 2 cups of dal, 2 eggs or paneer 50 gm, also preferably mix soya bean atta in your cereal, add butter to your dal and vegetable. Eat seasonal fruits and salads, go for regular walks in the open air. Keep a watch on your weight. I will recommend for constructional treatment and for regular follow up, for this consult dietician in person.