I think you need to ask yourself why. On top of that, you need to think about the possible consequences. STD's are possible even if you use protection!!!! If you get an STD, you risk endangering the life of, not only your wife, but your children. I think you should come clean with your wife. In one of my hubs I talk about the four key components in a relationship:
Communication, Respect, Honesty, and Trust. Without one of them, you have none of them.
By you cheating on your wife you aren't being honest, which means you're not communicating the problem, you aren't trusting her with what you should tell her, and you are definitely not respecting her. I am not bashing you, I'm just showing you that if you don't have one of these components, then you don't have any of them. What you're doing isn't right. Cheating is never ok, no matter what the circumstances are. You need to be honest and come clean. If you really in love your wife, you'll do what needs to be done to fix this. If you still love your wife, but don't know if you're "in love" anymore, you should still have her best interest at heart and want to do the right thing. It's better that she hears it from you than someone else; because, TRUST ME, all shit hits the fan eventually. She may not find out for another 20 years, but when she does, it will be that much more heartbreaking for her.