The concept of gender is a social construct. Humans are a complex matrix of innate and learned behaviour. Our prefrontal cortex hasn't fully matured until age 25, meaning you continue to change and develop your sense of identity until then. I don't believe for a second you had a strong, stable and unchanging realisation of self and ego at age 10. Part of human maturation is exploring these changes, testing psychological boundaries, and filtering and accepting external influence. We should definitely not be placing kids into any kind of boxes, either explicitly or implicitly.