Tic's, Fits and sleepless nights

My three year old son has never once slept through the night and suffers night terrors. He has quite a severe facial grimace and tic when he becomes excited with arm flapping and his speech will become repetitive. From a tiny baby he has suffered from episodes of screaming fits where his body will arch severely and go rigid- these can last in excess of 20 mins and he appears to have no control of this. He craves constant attention from me but will panic if approached by another child and suffers from extreme anxiety about so many things.

He is incredibly bright and has the vocabulary of a much older child. He has seen a pediatrician who has said he is developmentally forward but has offered no further help. My older son and ex husband have Aspergers but for some reason the Dr doesn't feel this is relevant. I worry for him when he starts school next year as his behavior is so challenging and without a diagnosis I feel he will be labelled as the naughty kid.

I would be really interested to hear of anyone elses experiences particularly the screaming fits - bizarrely enough although these used to happen several times a day they now occur in blocks where he can go several weeks with none and then it will happen daily for several weeks. Thanks