How to mend a relationship ruin my myself?

Sorry for the long message. Hope to get some (primarily female) opinions.. We're together for a long time and I love her dearly. I have never been unfaithful to her but, as a man, I did surf the net for porn and stuff like that. Last year I found a few forums with "normal" girls (not professionals) advertising for sex services. Out of pure couriosity I contacted some of them, chatted a few over msn. Though I exchanged contacted with these girls I never went out with any. I was too in love with my gf to do such a thing to hurt her. It was just a game. Once she discovered a note with some of the girls' contact on it and naturally she was heartbroken. I did manage to explained to her that I was just curious and nothing more. She had forgiven me and we were over it. Recently she discovered some old msn records on my pc that I exchanged with these girls and this time she was really upset. Understandably she thought I was lying to her and that I continue to go out with these girls. I am so ashamed and so regret doing this in the first place. Why was I so stupid to hurt someone I love so much? How can I convince her that I never did anything unfaithful? She said she will never trust me again. She virtually stopped talking to me and refused to talk about it. I know I have done wrongly and just wish to let her know my love had never changed for her and I am seriously about us spending the rest of our life together... This will be a scar in our relationship but I just wish to be able to explain to her the truth. Can anyone offer any help? I was so depressed and worried that I would lose her.

Anyone can help? Still much depressed..