For ways to get my 19 month old son to talk.?

My son use to say a lot of different words, now all he is really doing is really doing i saying a few words and holding his hand out and crying. I have been trying to tell him the words to have him repeat them but he will not do that. Does anyone have any ideas on what i can do to help him. He is already in birth to 3 but the do not feel that he has much of a problem. They are going to retest him tomorrow but i need ideas on what to do.