Baby acts starving! Whats up?

OUr new baby (9 days old) seems to be hungry quite frequently. WE are lucky if she will go 2 hours inbetween feedings. I do not remember my firstborn being this way. She drinks 2 oz. right now (we tried giving her 3 and she spit it right back up after she was done.) I asked the pediatrician about this and he asked me if she was fussy (only when hungry) or spit up, and she NEVER spits up (with the exception of the time we tried giving her 3 oz.) He said sometimes if a baby has acid reflux they will act hungry all the time because they want the liquid to cool the burning sensation. But he said it does not sound like she has this if she is not spitting up or fussy all the time. So I geuss my question is, how can I get her to go longer in between feedings? (3 hours???)