I agree with Wiseman, you need professional counseling to get past this.

Instead of the both of you talking this to death you need to find and set up an appointment with a marriage counselor. I would go as far as telling her she needs to do the leg work and find a marriage counselor she feels comfortable with and that you are eager to sit down with someone and try and to start repairing some of the damage that has been done.

She gave excuses for her behavior and like most shocked and stunned spouses you wanted to believe her because you love her. You are in no position to fix this yourself and you need to realize it right now. If you don't seek help you will continue to question her and set all kinds of rules to replace the missing trust and she will eventually resent you for it and she will file for divorce because you are controlling. It will not matter why you are acting that way, it will only matter to her that you are controlling.

You have an excellent opportunity to repair your marriage and make it even better than before but you need help doing so. She needs to answer some tuff questions and you need to hear the brutal truth about how she views you and the marriage.

Read the bottle the steroids came in, one of the side affects is not cheating...