I love my fiancee and want to completely trust her, but she has in her cellphone contact list the numbers of three previous love interests, and not just their cell numbers but work and home, too. She doesn't want to erase them, so I feel like she doesn't want to make a commitment. I know if I force the issue I would seriously damage our relationship, and I don't think it is worth that, but I can't be wondering, what if she is off with someone else?
Why limit it to her previous love interests? Why not worry that she's off with a colleague, or a neighbor, or some guy at the dog park, or that old friend of hers with whom there's no romantic history . . . yet?
You say you "want" to trust her completely. But that and a guy-free cell (like the double-entendre?) would provide only imaginary security, if that. Wanting to trust someone has little to do with actually knowing how to trust someone.
When you know how, you know that everyone has exes, and colleagues, and friends, and neighbors, and there will be active suitors among them, and temptations in as many forms as there are stops in one's daily routine. You can't expunge all potential threats to your primacy.
All you can do is know that both of you will face temptations; know your own behavior and hers; know your own character and hers; and then form the most realistic expectation possible as to whether straying is likely between you.
You know how she is with and about these old love interests, right? You know whether she introduced you to them, includes you in outings with them, takes their calls when you're within earshot, sees them as close confidants or just once-a-year bland conversations? You know why she's keeping their numbers? You know whether she has integrity?
If all the data tell you she's a threat to cheat, then she's a poor choice for a spouse.
If all the data tell you she's unlikely to cheat, then trust that you did your best in choosing a mate based on the information you had.