i have the similar situation, my baby has just overtake his body weight at birth and i am breatfed 10-12 times per day (at least 20-30 mins each time) and give 2-3 formula supplement per day.
MCH doctor worries that he is underweight and also asked me to give formula supplement five times per day. Actually my baby sleep well and wet more than 6 heavy diasper per day.
18/12 3.165kg
23/12 2.99kg
29/12 2.87kg
14/1 3.17kg
20/1 3.38kg