Do you feel that you're healthy? Has anyone else in your family expressed any concern about your weight? Calculate your BMI (unless you already know it):
http://www.cdc.gov/nccdphp/dnpa/bmi/adult_..._calculator.htm and if you are considered to be in a healthy weight range, then I wouldn't worry much about what the doctor says. It sounds like you eat enough and that you don't really feel concerned about your weight. You know yourself and your body better than your child's pediatrician does, who has known you, what...4 months? If she says something to you at the next appt, I would tell her to give a reccomendation to a nutritionist to evaluate things. I'm not sure when you typically start solids over there, but usually 6 months is when we start introducing them here. By 12 months, my DD was eating 3 meals a day and nursing at least 1/2 of what she was before. Once he's nursing less,
if breastfeeding is causing you to lose too much weight (as the doctor thinks) he'll be nursing less and that should take care of the problem.