Technically that's what the "questioning" category comes from- the LGBT is just a very basic list, but there's a whole, huge spectrum of words that people use to describe themselves. Defining yourself is one of those self-searching journeys, you know? You talk to people, and you educate yourself, and hopefully one day you find a term and definition that you're comfortable with.

Barring that, you make up a new word. Or you don't limit yourself to just one. The words are supposed to be flexible, and they only exist to help you.