You see, I think, it's nice that you kind of "figured it out" and got to know that you were actually wrong the first time around. But... does labeling really matter that much? Of course, it's good to know who you are etc. but when it comes to sexual orientations, I sometimes get the feeling that people limit themselves too much. Does it matter if somebody is hetero-, bi-, homo- or asexual?
People simply need an identity. Labels are a method of putting that identity into words without dragging it out.
Heterosexual: "I like the opposite sex. ... No, I don't like Justin Bieber."
Homosexual: "I like the same sex as me. ... No, I still don't like Justin Bieber."
Bisexual: "I like both." This can very easily be dragged out into particular preferences of each persuasion
Pansexual: "I like everyone!" ("Wait, so you like hermaphrodites and shemales too?" This obviously deserves a punch in the face, but it'll still be asked.)
Asexual: "I like no one." (Frankly, I feel like this is basically sounding out, "I'm Batman," and it shouldn't be explained further because you'll end up with a Batarang in your back and/or crotch.)