Past Relationship Indiscretions

Several years ago I found the woman of my dreams. Problem was, she was not interested in the same. We were good friends and over time it blossomed into a wonderful, happily normal relationship. Unfortunately, during the time we first began dating, I had a couple relationships with other women I had kept from her. While we at that point had not discussed exclusivity, it was implied. She had had some rough relationships in the past and it had been a long while since she had trusted anyone enough to even date. I had resigned myself to never getting her by the time she revealed her feelings for me, so I had thrown myself at other women--who unfortunately I was still with at the time. The other relationships were over in the first month or two. We have since fallen very much in love and have begun discussing marraige.

Sadly my past indiscretions still haunt me. I deeply regret them and I know I will never betray her trust again. I have never met anyone as wonderful as her and I'm deathly afraid that if I tell her, part of our beautiful relationship will be lost forever. How could she ever come to believe me that I would never hurt her again? I find myself becoming increasingly paranoid of her cheating on me. I have no grounds, or any logical reason to suspect any such thing of her, and she has repeatedly expressed her distaste for those who are unfaithful. I believe it is my own mistakes that are wrongly leading me to distrust her. What can I do?