well, in a relationship secrets is not a good thing it can lead to fights, break-ups, or even jealousy. Telling her the truth will show trust, love, faith, and courage no matter how bad it is. Past is past if she can't accept it then it's her loss. It's not like past happened during the relationship.
Yes. No matter how bad it may be, you gotta be honest with her. I know its hard to because I've been there, I know what its like to tell the one you REALLY like. But you'll be glad you did it in the end. BEST OF LUCK! ~Don't forget to follow:)