Those of you who have children DIAGNOSED on the autism spectrum, what were their signs as toddlers?

I have a feeling my 19 month old son may be on the spectrum. He has a doctor's appointment in a week so I will be asking his pediatrician then. But I have anxiety and I'm 31 weeks pregnant, so I'm getting kind of anxious during the wait.

Things that make me think my son may be on the spectrum:

He hasn't spoken his first word yet,

He doesn't point or clap,

He flaps his arms a lot,

He's extremely independent, like he will play in his room on his own literally all day even though I have his door open.

When he is in his highchair, he will obsessively throw himself back so his head and back hit the seat. He's done this since he was 6/7 months old. He also does it in his bed before he goes to sleep and randomly against walls in the house.

Squints, grits his teeth, and shakes his fists (all at the same time) randomly and for no reason.

Will randomly stare at objects we've had in the house forever and cock his head at them.

From about 5 months old to 16 months old, he would obsessively stare at his hand like he had never seen it before. He would turn it over and over and just stare at it for several minutes and it happened a couple of times an hour for like 11 months. It happened enough that everyone who saw him then would comment on it.

Doesn't seem to know what any words mean when I say them, including "no." My first knew what no meant by 9 months and would listen. My 19 month old does not and it doesn't affect him at all. (Like when I am putting up groceries and he is trying to play in the fridge, I take whatever he has, put it back, tell him no, and redirect him. But he will keep coming back over and over until thr fridge is shut. He doesn't get angry about it or laugh like he thinks he is being funny. He has no reaction to it.)

Only started showing an interest in playing with his 3 year old brother this past month. And the only thing he really cares to play with him is chase.

Hates when anyone touches him or gets too close. Used to hate to be held until this past month, but asks me to hold him now (by holding his arms up) and that only started this past month. But besides when he asks to be held, still doesn't want to be touched, hugged, kissed, or have anyone sitting close enough by him to touch him.

He's met my sister's newborn and showed no interest, like he didn't even notice she was there. He does this with animals too. He does it with our cat we've had since he was born, with my mom's dogs when he met them, and with a baby kitten we fostered for a while. He shows no interest at all. And if you show them to him or my cat tries to rub on him, he just pushes them away like he does when he feels like someone is invading his space.

He gets obsessed with certain toys and will ONLY play with those for months, nothing else. And he will do it all day, for hours. Last time it was puzzle pieces, but only the pieces. Not the puzzles themselves. He would just carry about the pieces all day long. Now, it's three different balls. He will bounce them in the kitchen all day long, but will now express an interest in other toys for a few minutes before eventually going back to his ball.

To those of you who have children who've been diagnosed, what signs did they show as toddlers? And does my son sound like he could be on the spectrum? Like I said, he has a doctor's appointment next week where I will voice all of my concerns with his doctor.