How do I address his emotional cheating?

My mate with whom i have 3 kids is having an emotional affair with his supposedly ex who lives in another continent.He doesn't know I am aware of it. she email nude pics to him and professes undying love. She' s determine to wait for him no matter how long it takes for him to come visit.I don't see any replies but from her mails he does call her. My trust in him is so shaken, but i still love him. Each time i stare at him, especially in bed ,I wonder if he's thinking of her. I have all her contact informations and pictures. How do i address the issue?