Possible autism or just a typical 3 yr old

My son was always a quiet baby, kind of serious, slept most of the night until about 2 1/2. he would stack blocks and play with toys, but when the blocks fell or just for no reason that i could see, he would get frustrated with his toys and whine and knock them over. he is now almost 3 yrs old.he has a vocabulary  of 3 words. he stares off into space a lot, he wont potty train. but he does smile and play and laugh and play with other children. he is social and will even walk right up to a stranger and want them to hold him. he has started hitting himself and i mean as hard as he possibly can. when he gets mad he looks around for things to throw or knock off of the table. his tantrums are worse than anything i ever had to deal with with his other two siblings. does this sound like possible autism.

[William L. Holcomb, Ph.D., BCBA-D]

A month or so ago I answered a very similar question, and this is basically what I wrote.  The first question I ask almost every time I hear about a child like your son is: have you already taken him to the pediatrician, and what does he or she think?  Did your son’s pediatrician think something was different enough to refer you to a local Early Intervention Program (EIP) for further assessment and treatment?  If you and the doctor feel that you son may have an autism spectrum disorder (ASD), I recommend that you try to find a clinic that specializes in children with ASDs for further assessment.  Talking to your son’s doctor or the local EIP may help with this.  I don’t know where you live, but in the US, as soon as a child with a suspected developmental disability turns three years of age, the local educational authority (usually your local city or town school) is responsible for doing an educational assessment to determine if the child qualifies for special education services at that time.  Again, if he is seen by the EIP, they can help with a transition to these services.  You should check with your local government social services and educational agencies for the procedures where you live.  

Also, some of the other behaviors that you mentioned may or may not be indicative of the early signs of an ASD.  Below are several websites with information about ASD.  You may find it helpful to review these sites to see if you think you need to take your son in for further assessment, etc.

About.com Pediatrics
http://pediatrics.about.com/od/weeklyquestion/a/04_signs_autism.htm
American Academy of Pediatrics
http://www.aap.org/healthtopics/Autism.cfm
First Signs
http://www.firstsigns.org/