17 month old still not talking

My baby boy is 17 months old and still not really talking. he can say mama, Dada, our dog's name, and no. but he doesn't very often. he can obviously understand what I'm saying so I know it's not a hearing issue. he is super shy but makes good eye contact and is super cuddly. I ask him to give me a kiss and he will. I ask him to retrieve a toy and he will. he babbles all the time. he is an intelligent guy but I think he just doesn't feel the need to talk? we communicate really well without words. His doctor wasn't worried at 16 months and I see her again in a month. any other mamas in the same boat? when should I worry?