Cheating Confession...

My Husband told me that when we were dating for 4 months he cheated on me for a month he went on dates even kissed a girl. After that month he knew he loved me and only wanted to be with me and we dated for a year before we got married. Now almost 2 years into our marriage he tells me this? I was in complete shock couldn't believe it! Wish he had never told me if I knew then what I know now we would have broke up right away. I'm happily in love with him but this news is beyond upsetting. What do I do act like it doesn't bother me it has been like 2 years? What do I do. When he told me I just cried I never would have ever thought he would cheat? He tells me he's completely faithful to me. What would you do if you were told this?