EBF baby slow to gain weight

Kristie
Our beautiful baby girl was born 9weeks ago now and everyone still comments on how "small" she still is! She was born 6lbs15oz and then after leaving the hospital took a month to get back up to 7lbs- a lot of this was fault of my own as my milk didn't come in for a week and by that time we were struggling with her latch since we had to supplement with bottles in the mean time. Now that she's finally been EBF'ing, I feel like she's playing a game of catch-up weight wise even though I feels she looks and acts perfectly healthy (very alert, 6-7 wet diapers and a poopy one almost each day) I do always give her the breast until she's either asleep or pulling away to make sure she's full. We just had our 2 month checkup yesterday and she was 8lbs5oz but her pediatrician still seemed concerned about her weight. Just curious on how much we should be worried- Her doctor just wants us to come back in a month an recheck her weight. Any input would much appreciated ladies :)