I am Bisexual I know. I have only been with guys till now and whenever I have a date home, I usually feel it and get hard without any problem (I've slept with interesting guys). Last night, I cracked a date with this hot girl over at my place and basically my first time with a chick but I was too nervous may be and she wasn't that interesting either. I didn't feel the chemistry and hence no hard-on even when i thought about kissing her. Damn! I'm so confused!! The first thought that comes to my mind is that may be I'm gay. But no, I have jerked off to straight porn and thinking about girls, it's never been an issue. I don't know but it's definitely taking all my attention off lately. Has anyone been in such a situation?
I haven't bee in this situation before, but it was probably because you were nervous and there wasn't chemistry. She may have been hot, but you can't force yourself to like someone if you really don't. And the nervousness being that you have only been with guys. I wouldn't let it worry me.
Hope I helped!