How do fatherless women cope with insecurities in relationships?

I know that everyone knows that women who grew up without the security of a father tend to be insecure in relationships, and somewhat needy. I unfortunately am one of those women. As much as I hate to admit it in the back of my mind I am always wary that my fiancee is just going to leave me one day. My fiancee and I discussed this and I just feel confused. I think that my fears of abandonment are justified because I have never met a man who could love and stay with the same woman forever. I however do not want this to effect my relationships negatively. I would really like to hear from women who know what I am talked about and maybe have a suggestion on how to cope.