"To My Fiance; I'm Sorry I Cheated on You."

To my fiance I am sorry that I cheated on you with my ex just 3 months after we had been together. (Back in 2012) I was at a very emotionally confusing and vulnerable time and did not know if I wanted to return to him or stay with you. I eventually realized (it only took a week) that I am better off with you. You treated me (and still do) so well and were patient with me. Every time I would lie with my ex, I would feel unbearable guilt. I knew it was wrong, but I did it anyway. The only reason I even forgave myself was that I told myself that I'm only human and that if I didn't, I'd go insane with the guilt. Also that I set myself straight and told my ex I never wanted to see him again. He begged and pleaded for one more chance but I said "No you had your chance but I am with someone now who loves and supports me and not to mention I know no one would support our relationship after the breakup. People would think I'm stupid for leaving a guy who treats me so well and going back to a guy who broke my heart twice. So I'm done. It's over" I wish I could tell you the truth, but I know it would destroy the trust we have built so unfortunately I will never be able to tell. I am so sorry my love. I will spend the rest of my life doing everything I can to show how devoted I am to you now.