How Could I Have Wasted So Much Time?

I spent many days waiting on him hand and foot. I bent over backwards trying to make myself good enough to be his one and only love. We married and it was good at first. He was loving and caring, but somewhere along the way, things changed. I don't know what made the change in him because as far as I knew, things were fine between us. I feel like I may have done so many things to try and make "us" work that all of my work was done for nothing. What makes a man want to cheat on his wife or partner when she has done nothing wrong? Perhaps I was lacking in something that he wanted, but I would never know because he never complained. He seemed to be happy and I know that I put my all into our marriage. Did I waste 10 years of my life with someone who never wanted me in the first place, or did he just feel he had the right to cheat on me?