How do you confront a cheating fiance when you have proof but he will accuse you of snooping and invading his privacy?
Be calm, state the evidence that you have, and be prepared for
the possiblity of him projecting or throwing counter accusations at
you. It doesn't matter how you found out--his own actions have
given you the evidence of his behavior. If he starts throwing
insults or is unwilling to admit what's occurred, leave. What's
more important is the decision you've made about your relationship
and whether to end it or not. At least you have been shown his true
colors *before* any marriage, rather than finding out the truth
after you've been married or had children with him.