Emotional Infidelity

My last relationship ended dramatically after I was informed by my fiance at the time that he was having several online affairs. He was signed up to many dating agencies and was meeting girls online. He never met up with them, but they swapped photos and spoke for hours online. The relationship ended because I felt I had been emotionally betrayed and did not want to be in a relationship like that. Since then, I don’t think I have healed correctly and am unsure how to. I have dated since them but have developed a bad habit of not trusting anyone. It even goes as far as me viewing their emails to make sure this isn’t happening again. I have been in a really special relationship for about 8 months now but the niggling doubts are still there. I checked his email and saw that two months ago he swapped naked photos with someone via email. I feel awfful that I checked – I wish I hadn’t and I really wish I wasn’t the kind of person who does things like that. I feel totally betrayed. I know I am in the wrong for breaking his trust and checking his email, but since seeing the swapped photos that were sent when we had been together only 6 months and in a really (I thought) happy place makes me feel physically ill.