DS had 3 words and about 5 animal sounds at 8 months. At 13 months he had 15 words including "all gone" when he'd finished eating and "hot" if the radiator was hot or the fire was on so not just nouns. However for the past 3 months he rarely says anything other than Daddy and Mama and random sounds. He understands everything we say but he's definitely frustrated so I don't understand why he isn't using the words he knows. Has anyone else been in this situation where their child has stopped talking? Dont know if I should be worried?