I would try to not get caught up in labels of what you are and what you are not. I don't think sexual preference is a black & white issue. Labels are hard to shake. Sexuality is very fluid, especially if you have no real experience in either half of the court. It could just be fantasy. You won't really know until you explore.

Some people can be open to bisexuality for years then decide they've just changed and no longer like same sex or opposite sex partners. Some people claim to be 100% straight! Then meet the right person and find themselves VERY confused at new feelings of attraction. This is very common for people who have lived in an environment with very strict religious beliefs. It doesn't necessarily mean you were wrong in the past. Just means you may have changed your preference or your understand.

AFAIAC, I tend to define true sexuality by who you could see spending the rest of your life with; not necessarily who you are having sex with.

Hope that helps. Good luck!