That doesn't make you a homophobe. "Homophobia" (not a real phobia, btw) in today's usage means "hatred of homosexuals". Just because you are disgusted by the thought of performing homosexual acts does not mean you hate homosexuals. It strongly suggests you are not a homosexual - yes...but it says NOTHING about your feelings toward the acts themselves, or the people who are comfortable performing them.
Heterosexual "wiring" includes a pre-disposition toward opposite-sex, not only in their reaction to imagined sex acts, but also in their reaction to imagined relationships, and even in their reaction to imagining their society's opposite-sex relationship roles. When they imagine (or see) things other than opposite-sex, they automatically feel they are witnessing something that is "wrong", "disturbing", or even "disgusting". So you needn't be alarmed by feeling disturbed or disgusted. It is just a little-thought-of aspect of your natural guidance system that steers you toward your mate. It does not make you a hater...although some haters use that very feeling as their so-called justification.
(Interestingly, homosexual "wiring" includes the same sort of pre-disposition, but toward same-sex, AND the same sense of "wrong-ness" or "disgust", but when imagining things other than same-sex.)