I know what you mean! Both my daughters have been really slow weight gainers, and I've always struggled with this. I think there is just something in our mommy-make-up that wants our little ones to have that extra pudginess in case they get sick or we go through a winter of starvation, you know, the old, inborn biological instincts. That's my explanation, anyway. My 18-month old, who was born small as I had severe PE, but was not a preemie, currently weighs barely 19pounds. She eats well and is just a tiny one. Her sister, born at 34 weeks and less that 4 pounds due to IUGR, was tiny until she was about three. Now she's the tallest girl in her class and her weight is normal! It's hard sometimes for us to trust doctors, we've been through too much and are expecting bad news, trying to prepare for it almost, BUT we all know from our PE days that when doctors ARE worried, it's clear and they tell us. Right? So what I tell myself is if my pediatrician isn't worried at all, then my girls are fine. Tiny for their age, but marvelous. It sounds like your daughter is the same.