Hi,
No offence, please, but you had to attend to it long long ago. It's a strange situation: If she loved you she wouldn't behave in that way. I have the feeling that something is fishy here (I believe that she is hiding something from you). I don't believe you'll be able to attend to it by yourself so the only way remaining is get a marriage counselling. Please don't cheat, it might do much damage to you. On the other hand better prepare yourself to the worst case (you know what I mean, sorry !) I see it as the most probable case (and please don't let your love blind you).
Best regards,