Gah! Let me start by saying I'm so sorry you're dealing with so much stress right now! No matter which side of the coin you're on, infidelity is a hard pill to swallow.
When the person you love more than anything in the world betrays you (or when you hurt the person you love most) it can be devastating. Not to mention it can feel completely hopeless to fix!
Don't throw in the towel yet. There are plenty of things you can do to build a happy married life after infidelity.
End the affair. If you were the one who cheated, you have to end the affair and cut off all contact.
Go to therapy. Couples counseling is a great way to open the lines of communication and figure out what was at the root of what caused the extramarital affair.
Rebuild trust. This one is going to take a long time, but it can be done! Be transparent with your spouse and live up to your promises. Show them that they can trust you. (Still not sure how to rebuild trust? Don’t hesitate in getting a professional counselor’s help. Here’s how counseling can help you and your spouse deal with the emotional damage caused by infidelity.
Getting back to a happy married life after infidelity isn't easy, but is it possible! Good luck!