i want to file for irretrievable breakdown divorce?

my husband has been having an affair for almost a year that I have tracked via pictures, emails etc. he denies but as I have read since we have had a sexual relationship since I accused him I can't filed adultery as the cause of divorce. Sex is a bigger issue for him than me and has become problematic. Last November we discussed his seeing someone else because of my inability but after I went to a retreat I came back and told him that I wouldn't agree to that type of relationship but as it was very important to him, he should leave our home to have that life, he said he was fine with us. On Oct 14th I found out he hadn't been. He asked me to check in his email fo a letter he needed and I saw flight info for a person, but I assumed it was regarding a casket (hes a funeral director) then I saw the name on my son's candy sheet. Needless to say I investigated and found pictures, emails, flight info and even a reservation at the Poconos.