What does it mean when I have the recurring dream that my boyfriend leaves me for his ex or another girl?

It seems like I have this dream or a dream that is similar to it at least twice a week. We've been dating for about a month. He's in a big fraternity and I know girls are around him all of the time, but still he ures me that everything is okay, and that he's staying faithful. He's way different from the other guys in his frat, but the fact that he's even in a frat still bothers me. Plus he's got this crazy ex who will do anything to get back together with him. What does it mean when I have the dream that he leaves me for his ex girlfriend or another girl?