What do you do when your husband says he met his soulmate and is in love with her?

My husband and I have known each other for over a decade. We have been married for the past two years. Our lives have always been a bit difficult, being long distance for a number of years, in order to pursue follow our career goals, etc.

He began his higher education a year after we were married and has recently told me that he felt he made all the wrong choices in his life. That he has found someone that is his true soulmate – someone whom he as a deep and meaningful and strongest connection with, and that he married the wrong person. He has fallen in love with this woman.

He has told me he doesn't feel this connection with me, that he loves me but doesn't think he's in love with me, or ever was. I am beyond heartbroken, but also confused about how I could be such a bad judgement of character, and not have known my husband was not in love with me for over a decade. I don't know what to do and if I can ever get over knowing he poured his heart out in a love letter to her, announcing he's in love with her, and would leave me in a second if she were also to leave her husband and felt the same way.

We are complete opposites in every way and always have been, but I, along with everyone else always thought that was the charm of our relationship. I compare our relationship to a puzzle - while many married couples' lives are like pieces that just naturally fit together, I always feel that we are always pounding the pieces to fit into place. Is this a sign? Do we truly not belong together? We get along well enough, don't argue or fight too much but if we should be together, why does everything always seem so difficult?