Baby not gaining weight?


my baby was 9 weeks old and weighted 10.8. They said she was a couple oz short of what she should’ve been and try to feed her a longer period of time more frequently. I did this and today at her 11 week appointment she only weighed 11.5. The doc said she needs to gain more weight and said to give her formula. To alternate with breast and formula. My mom

Doesn’t think the doc should of jumped to formula. Does anyone has any suggestions or anything this is my first and I’m not sure what to do..