Low weight gain

Hi all , my little DD is 7 months old. She is only 14 lbs. She eats three solid meals a day 4-6 oz each time. I breast feed her on demand usually atleast 4 to 5 times . She seems content, but not gaining much weight. She refuses bottle ( tried giving bf , also tried formula).

She sleeps well at night may be one or two dream feeds. During the day she takes 4 naps 30 mins to 2 hrs depending on the day.

Pedi is not worried about the weight gain, I have a feeling that my milk is either not enough or does not have enough calories. Any ideas / suggestions from the lovely mommies will be great