Yes, you are absolutely still bisexual. In fact, many straight women don't enjoy straight porn or enjoy it much less than gay porn(woman/woman or man/man).
The thing is that there's more to the visuals of porn than just the images of genitals and intercourse. There's usually a male gaze perspective, a patriarchal, objectifying perspective of the woman in the sex act, even when it's subtle, and your brain will pick up on it even if you don't. It's easy, as a woman, to be turned off by straight porn and a lot of the lesbian porn around.

Personally, I'm bisexual(or pansexual) with what seems to be a slightly stronger preference for men. I find straight porn to be the least stimulating because of the stuff I mentioned above. The porn I watch most is in fact gay porn and it has nothing to do with my own sexuality. I also like lesbian porn made for queer women(by that I don't mean vanilla porn).