I Am Unhappy In My Marriage

I don't know what to do. I have been having feelings that something has been going on, with out any proof. I let it be. I went on with life. Then as I used his phone to call my mother, I saw it. The conversation that would show me the truth. The reality that I have been turning a blind eye on. He didn't know that I had seen it. He interrogated me as if something was wrong. That night I went to confront him about it, but before I could, he delete the message. I wanted to verify that what I saw was true. I used a teen safe website to hack into his phone. Sure enough, he deleted the messages. All of them, even some that I have not seen. They all came up on the website. Even phone calls, times, dates, and duration. I attempted to contact the girl on Facebook (Our family picture is on the front). She blocked me before we could talk. So I used my sister's to see her profile. I notice she was married as well. I decided, if I can't get through to her, then maybe her husband could. I sent him a screen shot of all there messages. He got the message the next morning. They both deleted each others messages, and both denied the affair. My husband still says nothing happened. Then accused me of over reacting. What do you say when you husband tells another women that he needs to hear her voice at 4:30am. And she is telling him I Love You. What do you do? I have done everything to keep my family at peace and together. All I wanted is for my children to be happy. I thought he wanted the same thing. Even after the abuse, I still stuck with him. How can I forgive this? Especially when he denies what's in black and white. I'm Catholic and I know marriage is a commitment and a sacrifice. I don't know how I can hold on.