why do MEN CHEAT?????

I was in a long distance relationship for 1 year and a half. I would drive 2.5 hours every weekend to see him (he's in the navy and couldn't come to see me), HE would call me every night and I never thought that he would be cheating. But it turned out there was a girl who lived closer than me that he was going to see every other night when I wasn't around. I didn't find out til after we were married. He had seen her for only 3 months and had ended it 6 months before we got married. His reason was that he had met her and thought he likes her, and he was stressed by the long distance relationship. But he realized he loved me and in the end that was why he stayed with me. I forgave him because we were already married and I knew he wasn't cheating anymore. At the same time, I also found out that he had slept with his ex 1 time before, right when we first started dating. I let that go because we had jsut started dating and were not commited to each other. Honestly I think sometiems men cheat to see what they can get away with, especially when they are young!