Are you sure that she is actually hungry when you are feeding her?
It is easy to mistake collicky crying, in the early days for hunger - and then top her up, which of course sets teh collick off again etc etc.
Have you tryed using an anti-collick medicine - like infacol?
Could it be reflux? Is she a possety baby?
Yes, babies do feed a lot in the early days, but it is best to check out that it is actually hunger that is the problem.
Also new babies sometimes hate being laid on their back to sleep. Both of mine slept on my chest as babies, with me semi-propped up with loads of pillows! They slept the sleep of the dead like that, but would be awake in a millisecond if I tried to lay them down!
You've come this far, so it may be worth persisting with breastfeeding a little longer to see if things settle down. As others have already said, formula may not cure the problem anyway - and if it is collic may even make it worse!