Developmental delays

Anyone else's child have some developmental issues with speech? My son is 18 months old and still not talking. He'll say mama, dada, and bye on occasion but that's it. His pediatrician said he's about 5 months behind and wants to set him up with a specialist. We try to work with him everyday and dont give him something when he grunts or points at it and we encourage him to use his words for things but he just doesn't. Anyone else's child a late talker?