did you husband tell you everyone he slept with?

So my best friend thinks I'm crazy that I have no clue who my husband has slept with. I know how many just didn't ask him who. Well Friday night we were hanging out with a group of people and the next day I found out from another member of the group that my husband had slept with one of the girls some time ago. Now I feel weird.  Maybe my friend was right and I should know I'm case we hang out with people again??? Thoughts??