If you experience any sort of romantic/sexual attraction towards men and women, you are most likely bisexual. The intensity of these attractions can vary and you might have a preference for one of the two, but it doesn't automatically make you heterosexual or homosexual. If you really feel like you're attracted to more than one gender, chances are you really are. I think that's the definite confirmation :) I hope my advice was helpful.
It's all based on your attraction. If you feel like you can be attracted to more than one gender, if thoughts and fantasies of this kind give you a good sensation, then you are bisexual! Your feelings, emotion and physical attraction are enough to determine it, there's no need to experiment or to date people to "confirm" what your body and heart already know.