Fussy eating, at my wits end!

Please can somebody give me some advice.

I have a four year old boy with autism. He has always been a fussy eater and it is driving me up the wall now. I get hassle from my family that he doesn't eat enough. And the stuff he does eat is "kid food" so like sausages, turkey dinosaurs etc. Most of the other stuff he eats is sweet stuff so like strawberry jam or chocolate spread sandwich, which then makes his hyperactivity worse.He eats very limited amount of veg. And getting him to try anything new is near on impossible!

It's all to do with how it looks and texture.

In the medical profession who is there that could help me with this?