Hello Spherical Flower,
I'm so sorry things didn't work out for you the way that you wanted. However, you might think about this: Better before the wedding than after it. As a veteran of more than one pre-nuptial break up, with time to give perspective to the situation, I've always ended up glad that things were figured out before there was a wedding. I've done it both ways and, though it may take some time for you to see things for what they probably really are, ending it before the wedding is by far the less traumatic way.
Wishing you well,
J Marcus