If you love her, give her another chance. That is, if she is willing to work on the relationship and move forward and improve it. I know how you feel.... You want to know everything. I think she is ashamed and humiliated to tell you about it. I suppose the why would be sufficient.
Me:49 W: 41 Kids=D14/D14/S10 Married: 15 Together: 16 Bomb: 08/26/09 Currently: separated but in the different houses.