Breastmilk = not enough calories

photogirl07

My son is a little over 3 months old and he is in the .24 percentile on weight down from .34 a month ago (that's .24 percentile not 24 percentile).  He was tiny to begin with but his doctor is concerned that he isn't gaining enough.  I EP and now she wants me to mix in 1/2 formula because she thinks my breast milk doesn't have enough calories.  Has anyone else ever heard of this?  I just got home so I haven't had a chance to research it.  Very disappointed