Visitor, I can relate to your question.
As a child I suffered from gender dysphoria, as well as having an inferior complex and severe introversion. I had an older brother who continually teased, harassed, and beat me up. The left side of my rib cage is still misshapen because of broken ribs. I also have a sister who is a year younger than me, and she was my mother's pampered little princess. I hated my life and felt like a loser because I couldn't compete with my older brother and felt ignored by my parents. I imagined that if I was born a girl then my life would have been much better.
As a young child I believed that all parents preferred girls. Girls were prettier, smarter, better behaved, and valued greater by society. I never thought I was really a girl inside, but I believed that being a boy was a terrible handicap. I started crossdressing when I was about 3 years old. I remember rummaging through my mother closet and telling her that I was playing mommy. I admired all the pretty things that my sister got, and they all were forbidden for me. I was jealous of my sister and all girls in general. When I got the opportunity to crossdress it wasn't sexual - I was just making my world right.
I no longer have any gender dysphoria, but I believe that my early childhood made permanent changes to the way my brain is hardwired. Now when I crossdress I can feel the release of feel-good neurotransmitters (dopamine, serotonin, oxytocin etc.) The response is automatic and involuntary. Crossdressing just eases tension, and makes me happy.