Relationship in jeopardy?

my fiance of 3 years 10 months and I are planning a wedding June 5, 2010. He says he made a mistake and he was dumb when he answered personal ads and sent emails to girls. I caught him by looking in his email because we know each others' pwords and I will be honest I am suspicious of these things. He is a great guy. Do you think a person can just be dumb a few times and really love you deep down? Please think carefully before answering, I really need some good advice