My baby boy is 5.2 kg only he is 3 months 10 days birth weight is 2.8kg an on breast feeding

A. Your child should be 1500 g more than the birthweight by completing the time of three months so if your child is gaining like this and this is fine but currently looking at the birth weight and the current weight seems a little less so I would recommend you to consult your doctor if needed start with formula feeding for your child