I am 5'7" and weigh 53kg. No matter what I do I never exceed 56kg and never come down below 52 kg want to put some weight. Nothing works out. Pls advise?

See Dr., then eat... If one is truly underweight (based on height, family background, and body type), a dr. Can evaluate for a hormonal, digestive, or other disorder. If no medical cause is found, then one can add weight by eating more calories of nutritious foods, while also doing weight-training to increase muscle. Proteins: egg white, chicken breast, salmon, ... Better fats: olive oil, peanuts, almonds, tofu, ....