Baby hasnt gained back the weight she lost in the hospital yet

I have been breastfeeding since my baby was born. Today she is 1 week old, and when we took her for her check up Dr said she hasnt gained any weight back yet. She was 8lbs 1oz at birth and is now 7lbs 1oz. She is always on the boob either feeding or just for comfort, and I have give her a few small bottles of breastmilk. I was instructed to nurse every 2 house now and go back next week for a weight check.

Has this happen to anyones babies before? This is my 5th baby, but this never happen with any of the others.