13 month old boy won't babble

Brittney

My son is almost 13 months, around 7 or 8 months he babbled ALL the time and said mama, dada, wawa, baba, kitty...then he just stopped around 11-12 months and he's back to blowing raspberries all the time. The pediatrician said she wants to revisit at 15 months because she thinks he dropped vocabulary to focus on gross motor skills. He is a big boy and hasn't officially started walking without assistance yet, but he gets around very well and is pushing all of the furniture and his toys around to walk. Any advice on how to get my little man back to saying words? I read and sing with him, he loves books!