20 months old, can not walk yet. Does not chew food, spits out solids. Will only eat baby foods and drink liguids. Sometimes does not respond to his name. Likes noises and pictures a lot, but can get very absorbed with things. Likes to spin all his toys, even ones that you wouldn't expect. Does like to stack things too, even though he won't stack his blocks. Is VERY afraid of the running water in the tub. He is a very catious child too. Most kids will just jump in while he seems to take his time with new things. Did have an issue with being constipated untill recently. He does rock himself overly much too. He naps a little too much too. People always comment on how good he is, but do think he isn't developing properly. He laughs and vocalizes a fair amount, but does not say words or speak in sentences. What may be wrong?