I think that what you’re describing may be more common than you think. I have sexual fantasies about men from time to time and I think that most of us are capable of it. I have always thought of sexuality as being on a continuum. Some people are gay, some are straight but most of us fall somewhere in between those two extremes. One could be gay, but notice attractive women and even have desires to engage in sexual activity with them, one could be straight but have gay fantasies from time to time, one could be pretty much fall halfway in between frequently attracted to both.