Cheating

I've recently managed to crack my man's phone code and found some pictures of a girl in our bed. When I asked him about he says he didn't have Sex with her and she was just stranded and he offered a place to sleep for the night. It all happened when I was visiting my parents. I was so mad at him for keeping this from me that I wanted him to leave. But then again I feel bad because I've cheated on him in the past and he never found out. Is this relationship worth saving?