Girls, hello! We saw a pediatrician, they said that for 3.5 months old…

Girls, hello! We saw a pediatrician, they said that for 3.5 months old we have a fast weight gain. At the moment he weighs 7 kg, and his height is 64 cm. Is this bad for the baby? Maybe someone has a similar situation? We're breastfeeding. We used to supplement him with formula until 2 months (there was not much milk), after that he refused the formula. Now we don't supplement anything anymore. Although we don't think we're chubby ?