*** determination is not a simple X Y chromosome, presto you're male or female. There's quite a bit of variability in there, and how it affects your mind in your development and results in your gender identification is something that is being studied and probably not well understood, but the fact that people feel different than what their physical appearance shows is a fact. People that are not straight do not behave in that way just to confuse _you_ or anger _you_, they exist and all the denial and simplification you want to believe is not going to make their existence disappear.
This video may be informative,
. Or if you want to go deeper, take a look at
*** Determination: Why So Many Ways of Doing It?
Rafael