I know this is a fairly old post but I’ll add what I recognised with my son incase it helps someone one day.
I honestly knew from about 3 weeks old. He constantly smiled at the corner of the room or at ceiling lights, I googled it and autism came up immediately (although I do know some babies do this and it not be autism but of course my son had more signs), he was a TERRIBLE sleeper like I’d never ever in my life heard of a baby/toddler sleep so awfully. When I told people he woke 30+ times a night they thought I was exaggerating but I wasn’t.
When he was 1.5/2 he started to have real bad sleep issues. Would wake some nights at 3/4am for 3-4 hours and then sleep from 7/8 until 11am. I remember one bad night he woke at 1am and we were so desperate to get him back to sleep we tried everything including a walk in his pram and driving. Nothing worked that night and he went back to sleep around 10/11am. I remember thinking this just can’t be normal. He’s been through stages of not going to bed until 1/2am too and it was hellish. We all felt nocturnal.
When he was a baby too he just was engrossed by the tv. He is nearly 6 now and he still is. He started to say words when he was 18 months old and I was so amazed but looking back (especially now I’ve seen how speech develops normally with my neurotypical second boy) everything he said was learnt from the tv, he never copied anything we said at all.
He would learn to wave and clap and then just stop. He never pointed, still hasn’t really if I’m honest. Again comparing to my second who points at everything imaginable to share interest. He never gave us toys to play with, never did imaginative play etc. he would enjoy emptying drawers more than playing with a pretend kitchen. He would love things like shampoo bottles to line up more than he would toy cars.
He was OBSESSED with the alphabet and numbers from about 18 months of age. Could count to 20 and knew the alphabet, order of the planets including dwarf planets, named all sorts of animals and random things way before he turned 2.
As he’s gotten older we have found he loves routine, doesn’t like when things are out of place. If a candle or ornament from the window ledge or fireplace has gone he MUST have it put back there. If he played with a toy for the first time whilst sat in front of the fireplace that’s the only place he will play with it for every time. I do suspect he has some OCD.
He is coming up to 6 now and has an EHCP in place at school, full time 1-1, still in nappies (but will do number 2s on the toilet now, just doesn’t tell you when he needs one) and we have FINALLY won the battle with the local authority to allow him a place at a specialist school where I truly believe he needs to be. He cannot follow a regular school curriculum for his year at all. He can now speak to get his needs and wants met for the most part, can follow very basic instructions but doesn’t understand how to answer questions or how to have a conversation.