I've had a threesome and my guy seems to think I am borderline bi. I told him that seeing other females turns me on. But I've never had any urges or felt as though i wanted to be with one. I love him to death. And its not like were out checking chicks out. Its just when we watch flicks.
It's perfectly normal for things to turn you on that you would never do. I get MAJOR turned on watching anal - Not someting I'd do though. A lot of women get turned on by lesbian scenes who would never actually do it. Don't worry about it.