Missed this earlier. TL;DR, be yourself; live, and speak, and act, and dress, and have whatever body you would prefer.
Gender and Gender Roles are entirely a fabrication of society; a tool that maximized population growth and preserved maximum reproductive capacity in a culture in the days of high mortality, by risking men more than women. They are as learned as a recipe, or how to speak Spanish, though equally real. Gender Roles are historically linked to sexes, but we're slowly getting over that bias; there's less judgement when Males (particularly but not strictly gay or bi ones) "act girly", or when Women are "one of the guys" these days. With medicine, preserving population growth against high mortality rates isn't a concern the same way either.
Sex is biological, and many people consider it more "real" or "concrete" than gender. We can use medicine to change some aspects of physical sex, but don't yet have extensive control over biological sex. However, all animals (us included) have the hardware for selecting and expressing as either sex; we're starting to find the genes that control an individual's sex, which some animal species use to completely change it even after reaching adulthood as that sex. When we learn how these genes and mechanisms work, it's very likely that one's biological sex could be just as arbitrary and optional as gender, or as dying your hair.
That said: I'd encourage you to define how you want to behave for yourself, rather than letting millennia-old social engineering like Gender Roles decide for you. Many folks are still going to be confused if your sex doesn't match your clothes, behavor, or gender; if you would honestly prefer being physically more like a different sex to any degree, and don't mind the present limitations of medicine and biological science to change that, there's absolutely no harm in that either. I don't see any reason a Male can't be a Gal, or a Female can't be a Guy; I think history won't either.
EDIT: fixed things. Phone formatting, yo.