Don't know if my step child is autistic .

My 7 year old son crys offten, can't tie his shoes, has a hard time hearing and following instructions, when my husband and I talk to him he looks as if the light bulb is off and when were around other people he acts really  crazy (twittiling his fingers, rocking and no eye contact). When  were out someone always ask if he's ok is something wrong with him. In school he's quite and does not particpate in class he can read and write but his comprehension is not there and his only friends are our 8 other children  and he follows the 4 year old and does what ever he tells him to do, he does not understand that he's the oldest .We have seen two doctors once when he was 4 and again when he turned 6 and everyone says he's fine, he's just a little slower then others ( well yeah I know that much but WHY) Please help me figure out what is wrong with my son?

[Sally44]

The good news is that if he is on the spectrum then he at the milder end.
I think the first thing you need to do is to have him assessed by a Speech and Language Therapist who has experience of autistic spectrum disorders, incuding Aspergers.
She should test his receptive and expressive language skills.  Sometimes they are very different.  For example my own son scores typical for his expressive language, but his comprehension of what is said to him, or classroom instructions are at around age 3.
There is a difference between language delay and disorder.  A delay means that language is developing typically but is just behind.  Disorder means that language is not developing typically.  In those cases improvements can also be made, but the underlying disorder is there for life.
So I would go to your GP and ask for the SALT referral and ask that he is also assessed by a multi disciplinary team that has experience of aspergers.
Then you need to keep a log of all the behaviours and speech difficulties you notice and write them down.
I would also recommend you look at some of the following disorders as they are typical of being on the autistic spectrum.
Semantic Pragmatic Speech Disorder. (not understanding the meaning of language - can be mild to severe).  Children also have difficulty understanding things like sayings eg. pull your socks up as well as sarcasm, humour etc.
Auditory Processing Disorder.  This is when language is processed differently.  Children may not hear sound as we do.  If your child mis-pronounces words or misses off whole syllabels eg. puter for computer then this needs to be checked.
Delayed Echolalia.  This is when the child repeats what has been said to them, or uses alot of phrases they have heard from TV or DVDs to make up their speech.  They may also have a strange tone of voice or may put emphasis on the wrong part of a word or sentence.
Executive Functions Disorder.  This is difficulties with things like understanding time, sequencing things, organising and planning.  A child may have problems following simple 3 step instructions, or may find it hard to start doing something ebecause they cannot plan what they need to do and in what order.
Sensory Integration Disorder.  You mention alot of sensory behaviour.  Twiddling with hands infront of their eyes, rocking, lack of eye contact etc.
All of the senses can be over or under sensitive or can fluctuate between the two.  Does he have any other visual behaviours such as liking mirrors or shiny things?  Does he cover his ears at sounds or complain about smells or tasts.  What is his balance and co-ordination like?  Problems with the sensory system could be assessed by an Occupational kTherapist and you need one with experience in aspergers as well as Sensory Integration Disorder.
He's probably playing with the younger child becasue that is the stage of his language and social development.  He will be finding it very hard in school.
You say he is reading and writing.  Is he reading without comprehension or does he understand what he is reading?

[Sally44]

If you click on the Health Page icon on the top right hand side of this page and click on Behavioural Characteristics Behind a Diagnosis of ASDs.  I have posted the clinical criteria under DSM IV.  This is a list of the behaviours the professionals are looking for when they observe any child.  Some parents have also put in examples of their own child's behaviours that gives examples of what the behavioural criterias actually are.  You may find this helpful in understanding what is considered to be autistic/aspergers.