hii my son is 3 months 22 days now his birth weight was 3.1 and now hes 5.2 is it normal or how much weight difference hes having how to increase his weight

A. Your child has gained 2 kg in almost 4 months which is very very good as a minimum expectation every month is about 500 g of your child has achieved that amount of weight every month so all if I look at the birth weight and the current weight this is very good