Should I be worried that my fiancee is going to cheat?

Recently my fiancee has been looking at my old conversations with my exes (3+ years old). She has had many more partners than I have and has agreed in the past to no longer talk or hang out with them. Recently though one of her exes has been showing up at work (we both work at Dunkin Donuts since we are still in college) multiple times a week and tries to talk to her for long periods of time. My fiancee wouldn't even inform him that she was engaged to me and so I told him myself. Shortly after she sent him a friend request on facebook even though he was one of the main guys that she agreed not to speak to again bc while we were dating he had sent sexual texts to her. I feel like she had also sent him messages on facebook and then deleted the conversation. Since then she has unfriended him (mainly when she realized how much I still dislike him) but he still comes around work. We both take promises very seriously so a already feel slightly betrayed. Should I be worried or do my fears show that I should no longer be with her? I love her and do everything I can to make her happy but I have been cheated on in the past and don't want that to happen again with someone I am planning on marrying.

Your fiancee's actions are speaking the opposite of what I would expect from a woman I was engaged to. You need to ask her why she didn't tell this guy she was engaged to you and you need to ask her why she even needs to talk to him at all. Of course you're feeling betrayed but I'm damned if I can understand why you would bother to be engaged to woman who doesn't even respect it..let alone you.

Yes, she is acting rather suspiciously but when you love someone, jealousy always exaggerates the situation at hand. Just be careful - you don't want to lose what you have because you overreacted. About the ex, talk to her about it and tell her how you're really uncomfortable because you're honestly jealous and really can't help it though you tried to. Thing is, when someone talks to their ex again, it's sometimes just friendly - especially since the guy comes to her workplace, as you said, everyday and tries to talk to her. Just talk to her and tell her how you feel though you might not want to tell her how you thought that she was going to cheat. Just say exactly how you feel.