i do understand, actually.
For many years, I wondered if I was a lesbian... because I always find girls more attractive than guys, and I always check out girls and almost never do that to guys on the street. I am also very open to kissing girls and doing things to girls.
At the end of the day, why does it matter what you label yourself? If the right person shows up, and you're comfortable with carrying on something (relationship, a fling or whatever) with him/her... why does it matter what his/her gender is?