M.T.
I wouldn't really worry about it R.. Despite what your ped says, the pediatric authorities have been recommending not starting solids before six months for some years now. He really doesn't need any food. Up til a year old, their milk is their primary food and gives them all of the nutrition they need. Foods are just for tasting and experienting. Your 5-6 month old doesn't specifically need the food and I wouldn't go crazy trying to trick him into eating veggies, mixing in fruit, decreasing the fruit. It can take multiple tries for a baby to take a new food. At six months, he should only be eating maybe a tablespoon of food twice a day and never in place of his milk.
Good luck!