I cheated on my wife with a coworker. Should I tell her?
I'm assuming you're asking should you tell your wife. Because if you have to tell the coworker that you slept with her, your physical prowess comes greatly into question!
Absolutely DO NOT tell your wife. There are so many reasons why you shouldn't, but the major one is that it will be too big of a hassle. She won't trust you, you'll argue, she won't put out for awhile and more importantly, it will make it super hard to have another affair!
Quit being a pansy and also quit being so suspicious. The key to a good extramarital affair is not getting caught. Good luck and have fun banging the next chick! (Try your mother-in-law, that would be wild!)