4 year old repeats questions I ask him and doesn't answer

My son is 4 years old.  Everytime I ask him a question he just repeats it right back.  I struggle getting an answer from him on even simple questions. Here's an example:

Me = "would you like some milk?"

Son = "would you like some milk?"

He will keep repeating.  This has gone on for quite sometime. What can I do?

[RockRose]

Does he speak fluidly in other ways,  just not questions?  

Does he initiate conversations,  telling you about things he sees or has done?  

When you say "this has gone on for some time",  does that mean he used to be able to answer questions appropriately and not just repeat them?

Google "echolalia" and see if this sounds like your child.