Talk to your wife and to a good divorce lawyer. Not necessarily in that order. Divorce may not be the inevitable outcome here, but you need to talk to a lawyer to know the lay of the land if it goes that way.
And when talking with your wife, try to have an honest discussion about where the relationship will go without getting overly angry or accusatory; it won't help. You both obviously want something the marriage isn't giving you now, and have for some time. Figure out a solution that works for both of you, whether that be an open relationship, counseling, or putting it out of its misery.