My lo is nearly 17 months and I'm just worried he's not very talkative. He can say few words but mostly doesn't. Feels like once he got over the excitement of being able to say something new he's not interested. He was able to say mama and dada for a while (can also point us on pics if we ask where's mama or dada so I'm guessing he knows meaning of them?) and recently been able to say yeah and no but will only ever say anything once in a while. Is it normal at this age ?