Divorce??? Really??? Why?

Im 28, in September my wife and I would have celebrated our 10th anniversary and we have one three year old son. My wife filed for divorce a month ago. When I was a teenager I occasionally viewed pornography, my wife and I got married at 18. Whille we we're dating she asked if I had ever watched it but I lied because I was ashamed and figured it wouldn't be a problem once we we're married. That was true for 4 years, but after a very emotional conversation about our sexual relationship where I expressed that I didn't feel close to her when we had sex anymore and that she seemed increasingly disinterested and she told me to grow up and get over it that its only sex, I again viewed pornography. I don't feel like it was an addiction it was very occasional a few times a year. I would always feel guilty and promise myself it wouldn't happen again. She asked me again if I had ever watch that and unfortunately I lied since I thought it would hurt her too much. A few months ago she started a new job, I senced a change in our relationship but wasn't sure what it was, after a month she tells me we can't have sex anymore and she doesn't think she'll ever want to with me. I told her I was willing to be patient while she figured things out. A month after that she tells me she thinks she might cheat on me and that she's never beeen happy with me, when she told me that I thought maybe we finally have some common ground and confessed that I had viewed pornography before and after our marriage but didnt want to ever again and I wanted to fix things. Her response was that that was cheating and she was going to divorce me. I found out later that on that day she went strait to another man who she is now in a relationship with. She swears they haven't had sex yet but says that its what she wants. How should I feel about this? Is this really all my fault like she claims? Im so scared about the effect this will have on my son.