You are certainly not an idiot, and you are right to have some urgent questions about your son's development. Without meeting you and your child, it would be impossible for me to arrive at a medical diagnosis or to reassure you that nothing is unusual. But clearly your little boy needs to be evaluated by a physician who can answer your questions.
I would ask your pediatrician for help locating a specialist such as a child psychiatrist or a pediatric neurologist who can perform a complete evaluation to determine the cause of your son's problems. Doing this now would be very important because getting the right treatment early is crucial in helping children obtain the best possible outcome in terms of language development and social responsiveness, which seem to be some of the problem areas here. His difficulties are not your fault and I am sure you will do everything you can to help him.