Forgiveness is hard. The key to getting through it is that you have to want to forgive.
Do you still love your wife? If so, the answer is obvious: sit down and continue this conversation with her. Take it as a blessing that she feels more comfortable with you now than she did all those years ago.
Also keep in mind that having multiple intimate partners before marriage has nothing to do with someone being monogamous and faithful to his/her spouse after it. Perhaps she saw this as a little white lie, told to protect your feelings. Or perhaps she was afraid of condemnation on your part. Talk to her. Let her prove you can trust her now more than ever.