Breastfed babies DON'T usually match the standard growth charts, and you're lucky to have a doctor who is aware of this and is reassuring you. Unfortunately, the standard growth charts that have been the reference for decades, AND ARE STILL USED BY MANY DOCTORS, are based on a study conducteed in Ohio from 1929 to 1975, where the vast majority of the infants were formula fed, and, according to one account, there was also very little ethnic diversity. Over the years, breastfed infants generally jumped into the high percentiles and then dropped below average. This disturbed some doctors and
sometimes these babies switched to formula, reinforcing the idea that a breastfed infant's growth wasn't quite "normal".
But this is how human babies are *supposed* to grow, mom's milk starts out super-high in fat to build the brain the first few months, then the milk gradually changes to a lower level of fat and the babies weight gain slows down. Cow's milk (the main component of formula) is intended to help baby cows grow fast thoughout the first year. Baby cows need to learn to walk almost immediately, and... there's not an awful lot of brain growth needed for a cow. They don't even have to be smart enough to hunt.)
Remember, ANY growth chart, even the ones based on breastfed babies isn not a test - it's a statistical distibution of *healthy* babies. The babies in the 3rd percentile were as healthy as those in the the 97th - it isn't just the middle ranges that are considered "normal" - anywhere in the chart is normal.
Your child is right in there near the center, so I wouldn't worry. (I have ridiculously healthy kid that hovers around 2-4%. No one worries about him because... he's obviously healthy - you can just tell.) "Look at the child, not the chart," as Dr. Sears said.
The CDC(Center for Disease Control) have started creating growth charts where the reference population have some breastfed children, at least proportional to the number of breastfed infants in the population.
Even better, the WHO (World Health Organization) is collecting data for growth charts for exclusively breastfed babies. (What a novel idea, huh?)
"Average Growth Patterns of Breastfed Babies"
http://www.kellymom.com/babyconcerns/growth/growthcharts....
(BTW - that avocado is a *great* first food - those are brain-building fats. I also started putting strawberry-flavored DHA supplement - Nordic Naturals - in his bottles of breastmilk around that age. Several years later, both my boys insist on having their "strawberry yummies" every morning.)
For info on starting solid foods, see
www.wholesomebabyfood.com