So many. The only reason I didn't figure it out earlier is because the only things I ever found were transphobic TV crossdresser characters and bad MtF genderflip fiction with a lot of cross dressing themes.
Being depressed, and my only release was playing video games.. completely unproductively, often doing nothing meaningful in the game.. with female characters.
Spending a lot of time (fruitlessly) searching online for genderflip fiction with female characters put into a male body, since that seemed like something I NEEDED to read. For I don't know why.
Ended up sexting with a gay guy somehow and ended up basically fleeing because I went straight to she pronouns and couldn't get myself to switch back, and of course he wasn't into that.
Tried writing fiction with a mix of male and female characters. The male characters I couldn't figure out though, they seemed hollow.
Getting in trouble in English classes oh so many times because I kept using "They" for everyone. Because when I was young, I got it in my head that using "He" and "She" was obviously insulting to people, so I couldn't imagine inflicting that rudeness on people.
Did roleplaying online, using a male character. In the early 90's. Someone accused me of being a girl playing a boy character badly. Soon after, I gave up playing male characters mostly. I had a few but they felt much more like caricatures.
I went for dancing lessons. The instructor demanded I ease off on the waist movements and dance like a guy. I basically stormed off and couldn't go back.
Decided to study martial arts, because well.. guys are terrifying! Being around them is a bit like walking into a pop test in a subject I didn't have any study materials for, proctored by thugs with baseball bats ready to beat anyone who fails. Was horribly repulsed by all of the arts based around physical strength and direct force, I could only make myself study very 'feminine' ones. Spent a huge amount of time and effort working how to do every technique with as little physical strength as possible because it felt so very wrong to be able to do things with strength and mass and I was sure it would go away. Eventually, more or less stopped practicing because I got a look at some of my muscle development and freaked out, then had an anxiety attack at the idea of building up my shoulders, with "not enough shoulder strength" being the number one thing holding me back in advancement.
Feeling like a fake, all the time. Feeling constantly like a pilot of a huge meat mecha like a huge animatronic Godzilla incapable of showing emotion. Being constantly upset because things would make me cry, but my body... wouldn't. I would have to spend a huge amount of energy trying to force tears, and I could never get enough out to be cathartic.
Realizing that when I would fantasize to myself, that my vantage point wasn't from the side looking at the girl, it was from the other side.
Taking dream logs down for a counselor and having a casual note for no particular reason that had any effect on the dream "I am a girl" on more than half of them. The counselors would comment on it a lot but refuse to say why they found it interesting.
Sports talks? Terrifying.
Last straw right before the dam exploded? Trying to fill out a form at the IRS office, reaching to check the "M" box and freezing up for a full five minutes at the wrongness of it, unable to mark the box. It happened again at school the following week. I ended up filling in "Other" and not knowing what to put in the blank.
And I am glad that dam exploded, because I was really worried about my partner being reduced to rage and crying whenever he would go clothes shopping in the women's section, or get a haircut that was yet again just not short enough, or his rages about his chest.