God Bighands....I am so, so sorry. I wish I could offer you more than that.
I understand precisely what you mean by having a heart-overruled-brain. I spent the better part of the relationship with my ex denying to myself over and over again that she was cheating on me, making ANY rationalization I could to make it seem otherwise. It only serves to make it worse when the illusion is shattered.
Please know I am keeping you in my prayers, and if you need me for anything, my PM box is always open.