I need advice Mature Women & men?

I've been dating my now fiance for 3 years now [he's 26; im 25] So far everything has been great..up until Yesterday. He left his Gmail account up & me being the nosey person i am didn't expect to find anything so i looked thru it...I find Messages dating back to march 2011 from him trying to meet women on Craigslist "personal ads"....I asked Him about it & he just says he sorrry & he never met anybody on the website.. he just emailed.Which i DO NOT believe.. I just need advice and or Words of comfort.. Help a broken hearted woman!!!