21 month old not talking

I want to know if other mamas are in the same boat .. my son says mama dadda , dishy (fishy) holy , ball and a couple other things .. but compared to some kids his age he doesn’t communicate the same .. I notice a lot of the time when he wants something he will scream ( like a squeal ) this just started . My doctor said to wait a couple more months and see if he starts talking more he also has a hard time doing puzzles and things like that . Just wondering if this is normal or is he behind ! Help