<human>: Reddit lurker for ages, but this is my first real post. I've sought advice from close friends and family, but I know Reddit typically has all the answers.

I've been with my boyfriend for more than four years. In August, a month before we moved in together, he made an account on Plenty of Fish and started messaging girls in his area. This escalated to texting and eventually sending naked pictures. He says he never met any of them in person.

I noticed he was acting strange. Texting less, no sexting at all, rarely Skyping. He seemed distant. When we moved in together, initially I was really excited, but our sex life sucked and I cried a lot. I kept asking what was wrong and had no idea about the messages.

Two weeks in, I was up and ready for school when I noticed him texting. It was early, so I thought this was strange. When he got in the shower, I felt compelled to check his phone (I never snoop, I never thought I had reason to, but I noticed he had been weirdly protective of his phone and wouldn't ever let me touch it).

Go figure, I find extremely detailed dirty texts. Later found out about photos. 

We decided to stay together. We live together. It didn't really feel like a choice. Four months later and I've put on weight, don't like myself, cry during sex and often feel spiteful towards him. But I've loved him for four years. He's been a wonderful boyfriend lately, no more messages (to my knowledge), but I'm struggling to move forward. What do I do?

Can you provide a brief overview of the text?
<bot>: My boyfriend of four years sexted and exchanged nude photos with girls he says he never met. Is this cheating? How do I move forward? How do I stop blaming myself?