check up - i feel terrible!

Our daughter just had her 9 mon check up recently and she fell to the 15 percentile in weight! We have been feeding her a lot of breastmilk and also solids 3-4 times a day (i guess not enough food at each serving?!)... the doctor said we definitely need to feed her a lot more. It breaks my heart to know that this whole time we havent been feeding her enough! She never acted hungry & she is very very active & overall very healthy, but i cant help but feel guilty for her weight dropping so much 😢