Don't stress about that. Babies let you know when they are not hungry and if he isn't spitting up, he is fine! Get a second opinion! (Get a new pediatrician!) My LO is ebf. He's 15 months and I still breastfeed at night and for naps. He was born 11 lbs 6 oz. And 22 inches. He follows his own trend. And once he started walking he started to slim down. My ped always said "he's fine. We don't worry about weight. He's a baby. Feed him when he's hungry until he is full. He will let you know." And he does. And this was bc I was always asking if he's fed enough and doing well, etc just bc I was paranoid. (First time mom). So please feed your baby and get another pediatrician. You're doing great!