Could my boyfriends son be autistic?

I believe there may be something wrong develpomentally with my boyfriends son.  I have been doing some research online and he does exibit some signs of autism but not all.  For example he runs on his toes, he doesnt play with any of his toys he just lines up his match box cars or crayons.  He doesnt speak very well either for example he doesnt say Daddy can you put some music on he just says "music" over and over again.  He has a lot of one to two word phrases that he will say instead of using full sentences to tell you what he wants.  He does get upset over little things but doesnt throw extreme temper tantrums.  He also doesnt like to be outside of his own envirmonment for example when they come to my house the child seems to feel uncomfortable and wants to go home.  He isnt very affectionate and does seem to have a blank stare.  He has yet to use the potty and will run and hide when he does have to go the bathroom the child is 4.  Should I be concerend that there may be something wrong with him or could this just be a phase

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

Diagnostic criteria for Pervasive Developmental Disorders (including Autism, Aspergers, and others) include delays in social interaction skills, communication skills, and the presence of stereotyped or restricted behavior and interests. Based on your description, it’s hard to know which, if any, diagnosis fits, and direct (in-person) evaluation by a qualified professional is necessary for any diagnosis. If you haven’t already brought this to the attention of your pediatrician, I’d recommend doing so now, so s/he can help you decide whether he would benefit from further evaluation.  
Regardless of his diagnosis, childhood behavior problems like temper tantrums can typically be addressed through consultation with a Board-Certified Behavior Analyst (BCBA).  If you feel that the behavior is stigmatizing or interfering with more adaptive behaviors, you may want to consult with a BCBA.  This professional will want to spend time directly observing your child as well as interviewing your family, so that they can provide recommendations on how to best address the issue. A local BCBA can be found at the following site: http://www.bacb.com/consum_frame.html.  
Best of luck to you and your family