I was born into a conservative missionary family, so assumed I am a hetero female. I didn't know about anything other than the gender binary.
I had my Eureka moment soon after I moved to Thailand in 2010, while reading Transgender Voices: Beyond Women and Men. The book said your "gender identity" is the gender YOU think you are.
To my shock, I realized I thought of myself as male. Next, I realized I'd always known that.
Signs I'd missed:
When my childhood girlfriends became "boy crazy" I thought they had become boring and dumped them.
My best friends were boys, and I was the leader. They told me later they were terrified at trying to follow me as I climbed ever higher into the treetops to build forts, and only did it for fear of me mocking them for "being a girl."
My mom told both me and brothers not to "hit girls." At the time I only thought it was unfair, since my younger sisters were totally annoying.
My brothers and friends treated me as a boy. During school volleyball games, my male team mates would say to me, "Stand between those two girls and cover the ball if it comes your way."
I tended to compete with men and confront them. I didn't have a clue that cis females don't deal with men that way.
My reaction to a man looking me over was to immediately meet their eyes with an aggressive "What are YOU looking at" glare that caused them to look away, startled.
I only hung with men as pals, to gain a dance partner, etc. When I got married, it was only because as a loyal male, I couldn't say "no" to a pal.
I couldn't bear to see myself in the mirror or in photographs
I don't ever flirt with men.
My idea of having fun is climbing cliffs and wading in swamps taking photos of rare tropical birds and animals and selling them on mini stock photo websites.
My current car is a motorbike (I live in southern Thailand).
I have always dressed androgynously, and would get physically ill for two days after attending church when married, with kids, after having to present in a dress, hose and heels. Eventually, I compromised and only attended night services that allowed women to wear pants and casual shoes.
And I'm only 60% transmale!
I actually have a 40% female side that I must consider also, so I live as a non-binary partially transmale, or androgyne.