Have you considered the scenario that you might have a fear of settling down with one man? Or, that you prefer the excitement of a new conquest to the security of a loyal man? There could be several reasons why you want to wander.
Studies indicate that by two years into a relationship, the sexual excitement has pretty much abated between a couple. If that is all that a relationship is about, then the relationship is going to end naturally...no one's fault, just a natural end.
What are your goals as far as the future? Do you want a husband/life partner? Not everyone is capable of maintaiig a close relationship with a spouse/partner....that takes patience, social skills, dedication and motivation.
Probably, it would be helpful to you to clarify your goals. That should be the first step in sorting our your feelings about how you want to deal with how you make decisions in your life.
Best wishes!