Not only is that frustrating, neither of you are living an optimal schedule right now. Allow me to recap your question before answering further:
My baby has decided she wants to eat every three hours around the clock. I can’t sustain that, I’m just too tired. She is four months old. What should I do?
I will ask you a few questions to hopefully help with your situation:
Are you working at the eat/wake/sleep routine? You need to have these things in order to establish babies metabolism and help them extend the nights.
How long are you keeping her up during wake time? She needs adequate time for at least an hour and a half nap each cycle.
Is she napping well? You need to work on the day time naps and then the night time will fall into place.
Make sure to go back to the Babywise book and really read over the routine so that you are working at these things. Some crying is Ok to help her learn to sleep.
One more thing: be careful of answering every cry with food. We hope this helps. If you have more questions, please follow up with us in the comments below.