The doctor (Dr. Money) who created this idea that we "pick our gender" was a fraud.
In the 1960's he had a boy regendered as a girl (completely *all genitals removed) and he was raised as a girl never knowing that he was actually a boy.
He was forced to believe all the typical female girl ideas. Playing with dolls, not being agressive, etc.
But no matter how much they tried to force the gender, "she" would always show boy traits and want to play with trucks and "boy" based toys. "She" was more agressive. Etc.
Eventually the child became so agressive and depressed because he was being told he was a female and he didn't feel like he should. The parents finally broke down and told the child that they were born a male and turned into a female.
He instantly changed back to a boy and got a medically created penis. He finally felt normal and started to live a somewhat normal life. Except for the torment of what had been done to him which lead him into drugs. He eventually killed himself.
Gender is NOT a social construct!
People who claim this is a scientificly proven truth are basing their stance on THIS doctors corrupt papers.