A therapist is not a diagnostician, and autism is not diagnosed or ruled out based on one or two things a child can do. While people who say these kinds of things mean well, they do great harm to children in thier care because parents often delay necessary evaluations because that is exactly what they want to hear. Being willing to socialize does not negate the posibilty of an autism diagnosis either, both ideas are complete myths.
I have no idea what is going on with your son, and no one else will after reading your post, but you need an evaluation with a developmental pediatrician as soon as you can get one because something is definetly going on here there needs more than state mandated early intervention services. You need to know exactly what that is, it might not be autism, there are many different things other than autism that cause the kinds of flags you are seeing, and you need a full evaluation.
Call the nearest children's hospital and make an appointment with a Developmental Pediatrician. It may take several months to get in to see one. As soon as you spend some time on the phone with the intake nurse, you will realize that you are in the right place, there are far too many red flags here for you to wait any longer. Never wait and see with developmental issues, your son has too much to loose if waiting is the wrong thing. You are in the best win win siutation possible. Either you walk out getting a professional saying that you have not a thing to worry about, or you find out exactly what to do so that your son will improve and progress in a more typical fashion. He wins either way.
In the mean time, call a private speech therapist and occupational therapist and start some private therapy for him, because they can do therapy with out a full diagnosis based on the issues you see. Public services are designed to make your son "functional" and will never be enough to maximize his potential, which is what you want for him. Get all the public services you can, but use it as a supplement for as much private therapy you can afford to provide.
M.
PDD is autism- othewise known as Pervasive Developmental Disorder. There are several kinds of Autism, or PDD. Usually, kids who do not fit the whole diagnostic criteria for atutistic disorder (classic autsim- or Kanners Autism) are diagnosed as PDD-NOS (not otherwise specified.) They may also be diagnosed as PDD-Asperger syndrome, Childhood Distintigrative Disorder, or Angleman syndrome.