Koltin at two months

We had Koltins two month checkup yesterday. He is gaining weight, but the doctor didn't seen to enthused with how much he had gained. I started to feel bad like there was something I was doing wrong. My husband opened my eyes that I am doing nothing wrong. I am feeding him when he is hungry and letting him eat until he is full. He did also have thrush. After doing research I found that it can be painful to them and it could affect their eating habbits until it is gone. The doctor gave him some medicine so hopefully it helps. In a month he only gained a little less than a pound, all of my friends baby's have gained more than that, I guess he will just grow at his own pase.