I am not normally a "counseling" advocate, but having a knowlegeable and loving third party invoved is crucial. Do it ASAP. Make the call first thing in the morning. You can work through this.
Also, get on your knees and pray tonight. Pour out your heart to God. He can work miracles in a marriage. I know--He worked a tremendous miracle in mine. My marriage was OVER. Finito. But God somehow put it back together and it is better than ever. He will do it for you, too.