i think my 4 year old son is autistic

I am very worried about my 4 year old son (he will be 4 in 4weeks).
He can name anything u ask him, but he doesn't speak in sentences. When he was 2 he started counting from 0 to 10 and he was counting down from 10 till 0, he wasn't just counting he knew what the numbers looked like.  He would point to our door number and say 2.
He also knew all his shapes even the hard ones like hexigon and pentagon and octagon. I wasn't worried then I seriously thought he was smart. 2 years later he's still no talking in sentences, when he wants something he simply says water or eat. He used to watch a lot of Tv and he only seemed to response to Micky mouse. He was seen by specialists 3 months ago, and all they said was that they wanted to see him in 6 months time.  The speach therapist visited him twice and noted that he had limited eye contact, and that he was one year behind with his speach.  He had his hearing tested and it was fine.  He plays fine with his brother and he loves other children, he doesn't know how to play with them, because of the language barrier but he still tries to join in.  He also follows instructions very well, for example you can ask him to get you anything and he would, he goes to the toilet on his own, his able to undress himself.  He can comunicate well when he wants something, like he keeps eye contact and try to make you understand only when he wants to eat or drink.
At the moment I dont know if he is autistic or not, if he is why didn't the pediatrician tell me, when she saw him 3 months ago she said she wanted to see him in 6 months time, that's in December.  Can you please help me, I feel really depressed and down all the time I don't know what to do.

[godsangels]

I definately would have him tested by a developmental pediatrician for autism.