slightly concerned

I have an appointment for my 9w old daughter next week. so I haven't gotten her weighed yet. but she's only eating 3 ounces a feeding of breast milk. I know this because when I go to work and my husband takes care of her, that's how much she's taking from the bottle. hardly ever does she drink more than 3 ounces. a lot of sources are telling me she should be eating 4-5 ounces a feeding... she eats every 2-3 hours btw. unless she's sleeping during the night. So my question is should I be worried? is there something I'm doing wrong? her output seems to be fine. And I'll definetly bring this up next appointment..