Alex, listen to hairdog. I just re-read your post and realized you've been together for 16 years! That is already long enough to know the truth - she will not change. You may think that she is "the only one for you". That is a dangerous myth, and it is just not true. For your own sake at least, call off the wedding now. Take a year (or two) off from each other and see other people. I bet you find someone you can be even happier with. Good luck...