does my 3yr old have autism

I am beginning to think my My 3yr old son may have autism but not sure. He has a speech delay whcih we have seen speech therapist for but still is a problem. He can get very angry and often will strike out at other kids including siblings if he doesn't like something or is told to do something. He doesn't really interact with other kids prefering to play next to them or by himself and I am not sure if this is because he doesn't know how to or if he really wants to. He seems to be happy by himself and will instead watch other kids or simply ignore those around him like he is in his own little world.
We tried to start kindy this year but he was really aggressive to other kids particularly when asked to do things by his teachers. Would not share equipment. We have taken him out for now.
He is obsessed with watching Ben 10 on tv and again will scream and carry on if something else is put on however will often calm down if is something he finds interesting but wants it on constantly which I don't want to do. have tried reading and doing acitvites instead but he just doesn't seem interested.
Always moving and just cant seem to sit still.  
He has no fear and will wander off all the time so I am constantly having to see where he is. His gross motor skills are pretty good but does have some trouble with fine motor skills like using scissors, drawing pictures.
He is a very affectionate child, happy to give you a kiss and cuddle.
I just don't know if it is normal or not?

[Jessica L Thomason Sassi, Ph.D., BCBA-D]

Based on your description I would say that you have some cause for concern, both because of his aggressive and destructive behaviors and because he sounds as though he shows some characteristics that suggest a possible autism spectrum diagnosis (language delays, possible social skills delays as well as somewhat restricted interests).  However, only an in-person evaluation by a specialist can determine whether the diagnosis of an autism spectrum disorder is appropriate. Whether or not an autism diagnosis is appropriate, it sounds as though you need help addressing his aggressive and destructive behaviors. I’d recommend that you describe your concerns to your pediatrician and ask him/her whether further evaluation is warranted.
Diagnostic criteria for Pervasive Developmental Disorders (including autism, Asperger’s, and others) include delays in social interaction skills, communication skills, and the presence of stereotyped or restricted behavior and interests.  Your description suggests that his language acquisition is delayed, and that there may be some delays in social interaction skills and stereotyped interests.  However, there is a fair range in what is considered normal (and it’s not clear without some direct observation whether his behavior falls outside of that range).  It sounds as though your concerns are as much about his problematic behavior – aggressive and destructive behavior – as the delays in social and communicative skills.  Whether or not your son is diagnosed with an autism disorder, you might want to consider getting some professional help addressing his aggressive behaviors. A Board-Certified Behavior Analyst (BCBA) will help you identify strategies to help reduce those problematic behaviors and teach more adaptive responses, regardless of your child's diagnosis.  A local BCBA can be found at the following website: http://www.bacb.com/consum_frame.html.   The BCBA will want to know more about the conditions surrounding problem behavior.  For example, you noted that he tends to have a tantrum when a preferred TV show ends (or you turn it off).  Are those the only times he has tantrums, or does he tend to have tantrums whenever preferred activities end?  This type of information will help the BCBA develop strategies for dealing with your son’s behavior.
Best of luck to you and your family.