Do I tell my little boy he has autism? Please help

He undoubtedly knows he’s different, but not why. He may not start thinking about it in detail until he matures, say around 11.

I personally think it’s a good idea to tell him he is autistic. That’s enough, if he asks what it is, keep it simple, and say it just means you think a bit different to other people. Again, that might be enough, he will ask questions as and when he feels like it. 
I told my daughter at around 10, becuase that’s the moment it actually clicked. She wasn’t diagnosed, I just knew. She was fine, and wanted to know more, so researched it herself.

Thank you for this.

Thank you for this.