you are not alone. The first time this happened, it really hurt me. He had been drinking, I was trying to ignore it, and he came down and picked a fight with me. Later he kept begging me to come to bed with him, and when I wouldn't he went upstairs.
It was picture texting. It was a girl I knew from high school (We are almost 40 so this is rediculous in itself). The texts started out sexual, she asked about me, he told her that we split up, and then she sent a picture of her pierced privates, he sent a picture of his, propped up on a busch light can on the desk in our office.
He didn't delete the texts, he knows that I look. He said he just did it because he was mad at me and felt like I was rejecting him. His insecurity.
It has happened twice since, once with the same girl and once with an ex of his. I also see that the only time he looks at porn is when drinking.