My 3 year old son is speech delayed and has a processing disorder as well as could be mildly autistic, according to his psychiatrist. Does this mean he is on the spectrum?

AUTISM SPECTRUM. Disorder(asd): yes, sounds like. Impairment in 2 major domains: 1. Deficit in social communication ; interaction; 2. Restricted, repetitive pattern of behavior, interests ; activities. Management: individualized acc. To age ; specific needs. Multidisciplinary approach to improve social functioning, communication ; adaptive skills; promote academic functioning/cognition ; reduce negative behavior.
Could be. According to the new dsm-v all children that are thought to be suffering symptoms of autism can now be conceptualized as being on the autism spectrum. However, the diagnosis needs to be reserved only for children that meet specific criteria that are fairly specific. Your child may benefit from the administration of an autism diagnostic observation schedule by an experienced psychologist!
Not necessarily. Impairment in social development should be present, your description did not say so.