I don't know how to help you on this but what you're doing to your wife is completely wrong. Before taking any step, at least think about your wife.
The relationship you are asking from her is only going to be temporary as you are already married and of course, that doesn't give her any guarantee of a future with you. Then why will she want to continue this?
Also, your wife doesn't deserve this. Clearly you should come clean to her. According to me, you have a few choices here.
1. Come clean to your wife, start afresh if she wants or end this with her for a healthy start.
2. End your affair for good and concentrate and invest in your family that you already have.
If you want this extramarital affair then my suggestion would be is end with your wife as she doesn't deserve this. She deserves the truth. And you can have a relation with anyone you like.
You have a chance to make it right. Hope you make the right decision.