I put the Doctor down as being asexual, but as we know, he can sometimes harbor feelings for his female companions -- best example being Rose.

Now, if she, the Doctor, were to find males attractive this time around and be exclusive with just that particular preference, I would find it understandable but wouldn't agree with it. I would prefer her being bisexual or things to be treated as pansexual.

Above all, though, the Doctor is a strong asexual individual. He had little to no consideration of putting things into motion when he did find someone attractive, as he knew the job at hand was his life and legacy, which for us, humans, would be in creating a family. The Doctor accomplishes that in a different way -- he creates a family in the companions he finds.