How does your child act in social settings like playgroups/playgrounds?

Don't take this the wrong way, but if he's your first child, you may just be over-yzing. I know from my experience that with my first I always did that--always wondering if something was wrong, if he was developing right, or as quickly as other children. You love your children and want them to be the smartest, fastest, most outgoing, etc. If you don't have any other children, it may be that he is just simply shy and not used to playing with other kids. My boys have two other half-siblings that live with us, so they always have interaction with other children and have had that since birth. I don't think you're crazy--you love and worry about your son. Maybe try getting him out to play with other kids more often, and if you already do that and still suspect something, take him to a professional and have him checked out. It won't hurt anything and it will ease your mind. If he is found to have some sort of an issue, by finding it early you'll have the best chance of correcting it now so he'll be fine later on. IMO, I think it sounds like you love your son very much and he's lucky to have parents that pay attention and are concerned about his development. :0)