My Wife Let Me Down, What Should I Do

I had heard rumours that a local youth had been seen coming of my house when I was at work.
I confronted my wife about this and she said I was talking rubbish. So I left it at that.
A couple of days later I was in a bar when some guys started laughing and looking at me.
I asked why and they said it was my wife I should talk to!
Again I confronted about this and she finally agreed that the youth who is 18….she is 46 did come round for a talk.
But said she nothing happened!
But I didn’t believe her and I kept pressing her until she finally admitted she felt flattered by his attention and that he had kissed her but that was it!
I was really annoyed and then we had a really bad argument and under pressure she finally admitted that they had sex. She said it was because she was lonely.
She said he had fucked her a couple of times since he first had her….and one of his mates had also called round ( obviously wanted to fuck her too) but she had only allowed him to kiss her and to fondle her breasts!
But she said it was over now with both of them.
I don’t know what to do.
I am shocked and still love her, should I leave her?
What type of woman does that with kids!