get to a doctor quick. along with that read to him. his interest may not be long, but that's fine. don't worry about that. his world is still brand new and full of discovery, so he'll be distracted.

but again reading and talking to him like a person will be very helpful. take him to the bookstore. they can help you locate books for his age. the topics won't really matter. it'll matter that you're interacting with him.

try not to get too frustrated. I'm sure its not an easy thing to deal with if he's not developing at the rate you think he should, but definitely catch a doctor asap.