Good morning, girls, my son was born at 3860, at 3 months he weighed 7…

Good morning, girls, my son was born at 3860, at 3 months he weighed 7600, at 4 months he weighed 9190, at 5 months he weighed 9 kg. I can't understand why he isn't gaining weight. And he didn't grow in a month. The pediatrician says it's normal, like he was gaining more than 500 g every month, I am worried. Every day I weigh him, he still hasn't gained any weight. What could be the reason?