My sons behavior

My son is turning 3 March 20. He doesn't talk much so we have a speech therapist come by twice a week and Early Intervention comes by my house once a week and goes to his preschool twice a week. This has been taking place for about 2 weeks. He also started preschool about a month ago. I have noticed an increase in his vocabulary and he has been making an effort to express himself lately. My concern is this thing he does with his mouth. He always has to make "beats" with his mouth all day along! It is driving me crazy and I want to know why he does it. He does it so loud and he does it while he is playing, eating, sitting by himself, laying down before he goes to sleep.He does it everyday all day. If he is not doing that he will start to bang on the walls with his hands or a toy. He will also bang his toy cars whenever he plays with them. He has an obsession with toy cars. Everyday at school the first thing he does is grab a toy car before he does anything and holds on to it all day. He is also obsessed with closing doors. He has to close every door in the house. Also before we leave his preschool he has to close the door, if he doesn't he flips out. He chews on his clothes and has been putting his hands in his mouth lately, to the point where he will throw up. He is potty trained. He has been potty trained since he was about 2 and a half. He can feed himself, he drinks from a cup. He is very sensitive, cries over everything. He is emotional and very very affection to everyone even strangers. He likes playing with other children, but still doesn't know how to express himself to them. He loves to be held all the time, he has to hug someone or kiss them repeatedly. He knows how to dress himself from head to toe. He doesn't like the sound of the bath, sometimes he blocks his ears. He has to have a routine, if he doesnt he flips out. Is this normal behavior? Pleas help, I just want to help him and know what I am doing wrong so that I can change and make him better.  

[Sally44]

The only way to find out is to ask his paediatrician to refer you to a multi disciplined team that has experience of diagnosing autism.  You say he is already having speech therapy.  Is this therapist experienced in speech disorders as well as autistic spectrum disorder?  A good therapist should be able to tell you whether his speech and play skills are giving an indication of an autistic spectrum disorder.  An experienced multi disciplinary team would include a Speech Therapist, Clinical psychologist, Educational Psychologist, and maybe an Occupational Therapist or Neurologist, depending on the child's difficulties.
You can also google the diagnostic criter ie. DSM IV Austistic Spectrum Disorder and see what it says.  A child has to have enough traits in each section to get a full diagnosis.
It is good that he is toilet trained and can dress himself, those are good self help skills that he has learnt at the right time from a developmental point of view.  However it is also common for children on the spectrum to have a 'spiky profile'.  This means they are 'typical' or even advanced at some skills and then really struggle or have virtually no ability in other skills.
I presume he has had his hearing checked.
You mention quite alot of sensory behaviour.  Google Sensory Integration Disorder to see if that sounds relevant.  I also found a book by a woman called Olga Bogdashina very useful called Sensory and Perceptual Differences in Autism and Aspergers.  You can google her name and read an article by her printed in Autism Today.  Her book has a caregivers questionnaire that you can complete to give you a sensory profile of your son.  Occupational Therapist are the professionals who assess and provide therapy for sensory issues.  Another good test they can use is the Winn Dunn sensory assessment.
His making a beat noise all the time could be a number of reasons.  It could be a rigid repetitive behaviour under autism, or it could be a sensory behaviour he uses either to distract him from other noises that bother him or because he needs more auditory input and he makes the beat noise to do this.  The body has to receive sensory information.  Infact sensory deprivation is a form of torture.  So if one of their senses is not working well they try to produce more sensory input.  And from the other end, if the sense is hyper sensitive to noise they can appear deaf (literally turn their hearing off), or cover their ears at noise, or make noise to distract them.   And with sensory problems their senses can fluctuate between under and over sensitive throughout the day and day to day.  So you will get different response to the same sensory input.  For example my son might cover his ears, appear deaf, enjoy popping balloons and enjoy going to drum club.  So it isn't as simple as a noise volume problem.  There is also Auditory Processing Disorder which can cause problems with auditory input and habituating to sounds.
My son's Occupational Therapist has just begun a listening therapy with him called Listening With the Whole Body.  There is clinical evidence that this therapy achieves results, so I am excited to be trying it out.  
But first you need to find out what is the cause, and the only way to do that is through assessments.