Only child. Neighborhood where I grew up was mostly retirees at the time, with a whopping two other kids in the whole development for most of my childhood, until we got a third. (Woo!) You want the recipe for 'introvert able to amuse the shit out of themselves in creative ways', well, that's pretty much it in a nutshell.
In some ways, I'm grateful for my differently-functioning brain. It took me a very long time to appreciate the simple fact that I would have doubtless been the most bored and miserable, sickly child, otherwise. If I didn't amuse myself, well, nobody else was going to do it. In some ways, I was lucky to a fault. My family is full of creative nutters. As infuriating as they all are sometimes, it was at least something they understood in theory, and when I talk about 'I will always be an artist in some form or another even if it means starving in the street' it's something I count as a tick in life's win column simply because it is one thing I can do, and that would not be the case if there had been no support or understanding there. (There's a downside to this one, though, too. Because of course there is, right?)
Elementary school was hell, but I don't completely blame the ADD. The school where I landed first was... calling it a backwater would be a compliment. My parents were raised in 'good' Catholic schools; this wasn't one of them but they didn't grasp that at first. I was tiny for my age, and we'll just say I was lucky I was a girl, because I guess tiny was 'allowed'. A friend of mine since those days, also small, but male? They threatened to keep him in first grade purely because "He's too short for second grade." This is the level of 'whatever y'all are smoking, you're bastards for not sharing it with everyone else.'
Being small meant being physically pounded on regularly while the nuns blithely looked on without budging; if you came to them bloody and in torn clothes from being dragged across the parking lot by an ankle, though, by gods you were the problem, not the kids doing the dragging. This was a separate issue, but one extreme enough I still have spinal damage from it to this day, and the ADD compounded it.
Being 'untidy' or 'disorganized' or 'forgetful' was simply bad. Willfully, intentionally bad, and could be nothing else. Once you were 'the bad kid', forget any hope of help. Forget the chance that anything going wrong is not completely and wholly your fault. That kid who turns around and smacks you so hard in the head you spit out a baby tooth while you're reading? Well, you shouldn't be such a bad kid, and these things wouldn't happen to you!
I remember 'the nice teacher' simply dumping my desk over onto the floor and telling me to organize the mess all through second grade. I remember other students stealing supplies that still had my name written on them in sharpie, and being told I was the bad one for not having them/'being unprepared'; any other possibility was unthinkable to everyone with any authority to do anything whatsoever to help. It spiraled, badly. Kids are not stupid. When even the authority figure indicates in some fashion it's acceptable to treat someone badly, they know it's just fine for them to do it, too, and there won't be consequences for it.
Then, because it was the way things were done there and then, when it was time for report cards, it would get worse. They had the 'socialization section', and by gods, do I hope that's gone the way of the dodo, and I was so grateful when, years later, public school had no such fucking thing. I was sick of 'doesn't live up to potential' by the time I was six. Every single box there was to check was marked 'Unsatisfactory' save for hygiene. To this day, the word 'Unsatisfactory' makes me want to spit and punch whoever's mouth it comes out of reflexively.
No, I actually don't want to 'make friends' when that very clearly means 'let people hit me or jump up and down on my back while I'm face down on asphalt'. Who the hell would? When a five year old knows this isn't the kind of 'friend' you want to have... If only the Evil Overlord List existed back then, is what I guess I'm saying here.
This is already long and this is... up to fourth grade. Everything from there gets so much worse for the next two year period I need to stop writing a while and just breathe and tinker with graphics for a little bit before even trying to tackle it.