I've always identified as straight, and have never had an experience with a female that I would call anything sexual or romantic.
However, I met my husband when I was fairly young, and have been committed to him for nearly 9 years. I think if I had had that "experimentation" time in my late teens/early twenties that's so common these days, I suspect it certainly would have included experimentation with women, and I'll never be able to say whether it would have amounted to anything more than experimentation. My instinct is that I am, in fact, straight, but I find women beautiful and sexy, though I've never had a deep down urge to fornicate with another woman, whereas I certainly do have the deep down urge for... <insert insertion joke here>. But then again, it could just be something I haven't been personally exposed to, and would enjoy if I did. But I'm married, and while I occasionally crush on other people-- usually men-- I don't really fantasize about anyone else. Well, sometimes. But actual touching is a big no-no.