All pre period, too! It wasn't a gender thing, it was a sexual development and puberty thing.
It was. And the gender aspect, according to the transactactivist definition wouldn't have made any difference. If you had identified as a boy, you would still feel the same.
But 'Gender' in the feminist definition IS involved.
If it was just about sexual development, boys would be experiencing the exact same thing. It's not intrinsically about that.
It's because girls, when they develop, realise that there is something of objectification going on for them. They're not particularly encouraged to be strong, powerful, sweaty, competitive. They're looked at, leered over, judged. Even if it's minor, it all seeps in subliminally.
There's no inherent reason for human girls to feel more self-conscious than human boys. But they do. Because of society's reaction to them.
That's the 'gender' part. The expectations imposed upon men and women.