In my case a combination of things.

My mom wanted a daughter. I was supposed to be that daughter but disappointed her. She would always tell me that she did not cut my hair and people thought I was a girl.

When my father was passing, I took a photo of my daughter along with other family pictures to his bedside. He looked at his grand daughters picture and said that was me in a dress. I said no it's my daughter. He told me that no it was me and mom used to dress me as a girl but stopped it completely when I went to school.

While in elementary school and middle school I would wear my mom's girdles, dresses and skirts. I was hooked.

When my mom was passing and in memory care, she confirmed the story dad told me.

In one aspect I have not progressed very far. I am still wearing girdles after all these years.