I know in my heart I'm about to marry the wrong person but I just can't seem to let go.
Is it something that you have thought about for a while?
I've thought this for a while now. Its just doesn't feel right to me.
Marriage is a huge commitment, if you don't feel ready it is not good to go ahead. It could lead to a very unhappy life.
I know of my hesitations. I'm going to do it anyway.
This is a major decision that only you can make in the end.   You seem worried, is there a possibility of delaying the wedding.