Thank you for the information and encouragement everyone. I finally found the calorie information. In case anyone else is interested, there are appoximatly 20 calories per ounce of breatmilk.
I will not let the Dr. bully me but in truth, I am a bit worried about thier weights also. Today when I spoke to her, she suggested adding 8 oz of formula per day to their diet. I am NOT at all happy with this suggestion. I feel I worked WAY TOO hard to keep them fomula free for 11 months to start adding it now. Anyway, i decided to pump more often and offer them more pumped milk from a cup. Right now I pump 2x a day and get 6 oz or so total but I'm sure if I pump more often I'll be able to get 8oz a day for each of them. Hopefully that will help.
to kama'aina mama - they were 4 weeks early but even measuring them againist 10 months old they are still very small kids.