I lived with my wife before I married her, and even I know I was wrong for doing it...but on the other hand, if I hadn’t, she wouldn’t have become a Christian.
Hard to figure out which way the see-saw drops on that one.
“And not rather, (as we be slanderously reported, and as some affirm that we say,) Let us do evil, that good may come? whose damnation is just.”
Joseph’s brothers threw him into the pit, and sold him to slavers. If they had not done that, Egypt would not have been saved from famine. So does that make what they did right? Hardly.
God could have saved your wife without your sin; he could have saved Egypt without Joseph’s brothers’ sin, as well. Just because God in His incredible mercy overcomes evil with good doesn’t mean evil is ok.
I am not assaulting you personally, because I (not a Christian at the time) lived together before marriage as well. I am just making what I think is a very important theological point.
Now, I guess that you've since repented of it and asked for forgiveness, since you've mentioned that your wife is now a Christian, and that is an extremely good thing, but don't taint the salvation of yourself and your wife by saying that your sins were somehow a good thing or beneficial in your salvation. To do so cheapens the sacrifice that Christ made for us.