Genesis 1:27-28 says that God created people as either distinctly male or distinctly female. It should be carefully noted that God did not create people and then let them decide what they would be. 
Gender is an "or" proposition, not a "both/and" proposition. Psalm 139:13 (referring to God) declares "...you knit me together in my mother's womb..."Deuteronomy 22:5 says, "A woman must not wear men's clothing, nor a man wear women's clothing, for the Lord your God detests anyone who does this." These are just a few of the Scriptures that speak against the idea that man should decide his gender and role within his gender. The entire Biblical context is that of men and women each operating within the biology given to them by the one true God who created all things.