DS is 19 months and very active and generally a happy little boy. He can say Ma Ma and Daddy and Bye Bye but he just won't. He understands everything we say and listens to everything so if we are talking about something and he hears shoes for instance, he will go and get his shoes, or if you ask him to get you something he will happily run off and do it. He also makes sounds all day but they aren't words. I'm just worried by the fact that he isn't saying more words or trying to use the few he does know more.