For as long as I knew myself, which I would say is around 3-4 years of age, I have wanted to be a girl. I can't remember how I first heard of the words "sex change" but when I did I knew that I wished I could get one. I might have been around 8-10 years old.
I had a "girlfriend" who I would go and play with when I was little, but we'd play with her toys. I had more fun playing with her toys - dolls, doll houses, etc. We stopped going there. I have no idea why. (I can guess why now.) I played house with my female cousin who lived next door. Played hopscotch, asked to play with jacks and other stuff. My parents were really hesitant and I think they knew but did their best to keep me on the straight and cis path. Speaking of which, I never really had any gay thoughts. Never was into boys or men.
When I was growing up we weren't flooded with media and information. We had no Internet. We didn't even have cable TV. Oh, we also had the library but it was in the city and I lived in a rural area. I didn't go often.
You know what one of the biggest triggers for me were? School uniforms. School uniforms were bland of course but they signified girlhood. I wanted that badly, so much so that I would sneak out at night and go borrow my cousin's school uniform next door from the clothes line, dress with it and return it before the sun came up. Nobody ever found out. I would even borrow our housekeeper's clothes when she wasn't looking. Why not my mom's? Mom and dad split early on. When I did go to mom's for the weekend/week, I did dress up in her clothes. I was in heaven. I was ME and it felt GREAT even though her fashion sense wasn't all that great. I didn't care, as long as I could be female, at least superficially.
When one of my cousins was in secondary school, she developed quickly, big boobs, hips and all. I was going crazy because she did and I didn't. My cousins wear a new outfit? I would get extremely jealous.
One of my dad's cousins enabled me and actually allowed me to dress up in girl sized dresses which were my size while I stayed there. I was overjoyed. We were careful to change back before my dad came to pick me up though. They even said repeatedly that I looked better as a girl. Again, I was in heaven. They "got" me. I really wanted to tell my dad so bad but I knew it would end really badly.
My teenage years were absolutely horrible. When the T kicked in, I don't know what the heck happened. I was a straight A student then I became a straight B and C one. I also developed a serious BO problem despite proper hygiene I could never really get rid of it. I was completely mortified to the point of crying over it a lot. I hated my body hair and would shave it and cut it a lot. In fact I even wanted to cut "it" off a couple of times. Oh by the way for my boy school uniform I would always choose the pants a bit tighter than it should be, because it felt closer to my skin and thus more feminine. That is until I went to secondary school and started wearing trousers instead of shorts.
Anyway, I did my best to suppress my dysphoria, burying myself in school, work, hobbies, politics (I worked in my MP's office) and finding a girlfriend. I succeeded at most, except one of the above, because I made so many "girlfriends" who were girls who were with my friends... sooo my clubbing days between 18-22 were basically girls nights out, me included.
Oh one more thing, I think it was even worse for me because I lived with my dad, I had absolutely no female clothes to dress with, except from my cousin, and I had to borrow it when I was home alone and my aunt was working outside.
Sorry for rambling on... but to sum it up, yes I knew early. Yes, it was and is persistent and no, it's not going away until it's fixed.