2 month old infant?

My 2 month old has been eating 6-12 oz of formula every 3-4 hours, is this normal? I feel like she's eating us out of the house, figurativly speaking. I mean she goes through a Parent's Choice size can w/in a week, sometimes less. The doctor said that she can have 1/2 tsp of rice cereal in her bottle, but that doesn't seem to be enough. She has regular BMs. I just don't know what to do anymore. Any advice?