Cadet will be along in a bit with an extensive welcome message with a lot of outstanding information. When you get it, read it all. It will help.
Second, find your own counselor. If your wife is in an active affair (and she is), then marriage counseling will not help. Marriage counseling only helps when both spouses are all in. but you sound like you need someone who will hear you and give you better perspective.
I am so sorry you're living this. It's no fun. But if you're willing, you can come through this better and stronger than you ever knew you could be, whether your marriage is saved or not.
Best to you.
Me42, H40 D12, S8, S7 A revealed: 7/13 Sep 4/14; Agreed to D 1/15