Is gender truly a social construct?

I don't understand why it's not seen as the social construct it, in part, is. I don't have any sources, but I'm sure it's well known that sex and gender are different, correct? Sex is biological, physical, and immutable. Gender is how you perceive your gender. Gender is mutable, in that if I say I'm a man when I was previously a woman, I've changed my gender. <br><br>My argument is that gender is socially constructed because of the idea that men are masculine and women are feminine. These two concepts are very much social constructs. I think it's very obvious and well understood that being masculine does not necessarily make you a man and being feminine does not necessarily make you a woman. But there is this expectation that women should be more feminine and men should be more masculine, thus giving the illusion that gender is equivalent to sex. It also gives the illusion that gender is immutable because sex is immutable. Gender is also mutable because people can be non-binary, where their sex is still immutable, but their gender is mutable and not necessarily masculine or feminine. Feminine and Masculine are expectations placed on gender, but they are not gender. Gender is still a social construct as a category, it is just that being feminine or being masculine is also a social construct as well. <br><br>The point is, the category of gender puts social constructs on you, which the physical trait of sex does not, and when you change your gender, you are changing how you are perceived and treated by society as a gender, not as a sex.