Babies nurse a lot during the first 6 weeks in order to increase your supply. Everyday at this age is a big growth spurt for them. They nurse often to insure that you will make enough milk at 3 months, 6 months, 9 months, etc.
Formula is much harder for them to digest so it knocks them out.... like after a big Thanksgiving dinner. I would never give my children formula simply because of the risks and illnesses assosiated with it. http://www.promom.org/101/
Good luck to you and your decision! There is also a breastfeeding board under the baby section if you need more help.