I am actually pretty similar to you. When i am turned on i really am attracted to almost anything, but when not, i have never really had a crush on a guy, or ever thought about being with one in a relationship. My upbringing was very encouraging to be whoever i want and i am very much a straight guy. I have a gf, and have crushes etc. only on girls.
The fact that i can get off with guys when im horny i dont feel makes me bisexual because it is a totally different thing. I would agree with the idea of exploring it and not trying to put a label on it, because really...some things are not black and white. And thats perfectly okay, as long as you are comfortable and being true to yourself.