Have you had an affair?

Did you get caught?
Confess?
End the affair and never say a word?
I had an affair over the summer. It lasted about four months and ended in September. I haven't spoken to that person since it ended, but ran into them yesterday in a store. I didn't speak, just turned and went the other way. I'm not even sure they saw me. 
No one knows about the affair. Should I confess or just let it be. 
Thanks everyone for the feedback!! I would never tell his wife and hurt her. I feel terrible about the whole ordeal and have definitely learned my lesson and will NEVER do anything like it again.