Should My Fiance's Sexual Partners Bother Me?

I already know that the question I am asking is narrow-minded. So, rather than being judgmental, please answer in a way that actually helps me.

Here’s my question: My fiance’ has had about ten sexual partners (that she told me about—could be more). This doesn’t include people who she might have simply “fooled around” with and not slept with. I never expected to marry someone who was a virgin (especially considering that I am not) but somehow I can’t stop thinking about this.

Sometimes I get images of her engaging in the act and I can’t stop thinking about that.

Is this something that should bother me? How can I get over this? I think she is a great girl and this should be a non-issue but somehow it is. What is this anyway? Jealousy? Insecurity? What should I do? Obviously, I can’t go into the past and change anything… and I know that this is the girl for me.