Sad&Angry- My Husband Had a One Night Fling

My husband cheated.

Long story short, there was no sex or any emotional affair going on. This was a one night "thing" that he states he stopped and walked away from. I'm sickened and have never felt so betrayed and unloved. He is trying so hard to make our marriage work. We have a son and I can't imagine taking him away from his father. I think it's important to stay strong and
try to make our marriage work. I believe our love is worth the fight and may make us stronger. We have been to counseling and our counselor said he did not believe my husband was a serial cheater. What he did kills me but can or will my pain and anger go away? Help!