Is being cheated on the most common reason to end a relationship?

Just broke up with my ex. We've been together for almost three years. I found out that he was being actively looking for someone. So I ended the relationship. We met each other in Montreal where both of us went to school. He moved back to the US last year and I m still working on my degree. We visited each other multiple times during the past year, and I spent Christmas with his family. He struggled to find a job after graduation (he is a musician), and worked as a server in a restaurant. Earlier this year, a friend of his helped him get a job as music teacher in an international school in China. Even though I knew it would be tough for us, I still gave him my support. It turned out that he betrayed me two month after moving to china. I was really chocked... I'm wondering how most people would do or suggest to do facing this kind of situation. Also if I was him, I would tell my significant other the truth and end the relationship first before starting looking for other people. I kinda know breaking up with him is the best choice, but destroying everything we've built together is so damn hurtful.