ADVICE: My Husband Is Always With My Mother, He Says my mom is sweeter; PLS I NEED YOUR ADVISE!

My mother is an attractive and interesting woman who dresses fashionably. Recently, I found out that my 39-year-old husband has been having s'e’x with her when he attends conferences at the resort near where she lives. When he told me, I was bothered by the fact that it didn’t bother me.