the only one who can decide this is you. and its nothing to be ashamed of, so don't worry.
i'd say that if you aren't attracted to males, whether mentally, romantically, sexually, or physically, that you aren't "bisexual" persay. many guys like to discuss penis size, masturbation, etc.
also, if you decide that you are bisexual, this doesn't mean you can't be with a girl or have a family with one. my boyfriend is bisexual and i'm fine with it. i just get to talk about cute boys with him now.
Hail Eris! KaAAIXTI! All hail Discordia! 23 Skidoo!
"If you're going to be a non-conformist, you're going to have to wear the uniform."