Newborn gained 5lbs in 6 weeks!?

Katie

So my baby was born at early, at 36+4 weighing 6lb 13oz on 8/23. He was 6lbs 6oz when we left the hospital. We were just at the doctor and he weighs 11.5 pounds at 6 weeks and 4 days old! He is exclusively breastfed and the doctor said it’s fine, but has anyone else had this experience? When did baby’s weight gain begin to slow? Will I have a 60 pound one year old?!? (Joking -kind of 😬)