Hello Oceanic: I see this is your first post here on PC. So... welcome to Psych Central.

I don't know as I really have any answers to offer you with regard to your concerns. Perhaps something happened that your brain has suppressed. Perhaps not. I think this is something you would need to explore with the help of a psychologist or mental health therapist should you wish to do so. While on that subject, though, here's a link to an article, from Psych Central's archives, that suggests memory isn't important to recover from trauma:

Memory Isn't Important to Recover from Trauma

I myself am 70 years old. So I also grew up no computers, no VCR's, no DVD's, etc. And I've had a life-long struggle with gender identity dysphoria. I don't have much in the way of memories of my childhood prior to the age of 8. But of the few I have, most of them relate to this. And, like you, I've always wondered where this could have come from.

I know the current thinking that gender dysphoria is caused by hormonal processes that go array in utero. But I don't know if I really believe that... at least not in my case. What it has come down to for me, at this point, is simply to have to accept some things just can never be known. And this is one of them. Perhaps that is the way your situation is going to turn out for you? It may well be worth your time & effort to try to delve into how you learned to do what you did. But in the end, it's possible it will all simply end up being a mystery you will need to leave in the past.

I hope you find PC to be of benefit.