I just thought of something, England. This probably isn't something that's an issue for you, but I recall a person I knew sometime ago who was in your position. Being an American, he had practically been weaned on the notion that he could only have one really true love in his life. So, when he fell in love with his secretary, he left his wife -- convinced he didn't really love his wife because of his passion for his secretary. That proved to be a profound mistake. In the end, his passion for his secretary came and went, and after it went, he was no longer married to his wife either.
Like I said, I don't know how applicable that is to either you or this woman, but I believe that if you perchance have been indoctrinated with the notion that you can only love -- genuinely love -- one woman, and that hence your attraction to this new woman means you do not love your wife, you should be cautious about acting on such a notion.
I personally think it is possible to love more than one person,i think though that the story about the Man and secretary is probably quite common.