Man, I don't have any idea what that must feel like. I have been dumped, but never betrayed like that. You are justified in your ache, but like others have said, forgive, and don't let it fester. I have seen the result of wrongs unforgiven and it isn't pretty.
Here are a couple of anecdotes, (neither of which happened to me) along your same lines, that ended well.
A friend of mine was a wild child and his current wife's Seminary Teacher writes in her yearbook to stay away from him. He cleaned up and went on a mission. When he got home, there were 2 girls he wanted to look up: current wife and one other. Current wife came to the airport and knew when she saw him that his pre-mission repentance was for real and she was essentially committed at that point. He looked up the other, her parents told him she was at a friend's house. He goes there and she's drunk & naked in the pool. Story ends well for him: beautiful family, successful career, positive impact on others, and service in the church. So much for listenting to Seminary Teachers on life advice.
Second guy I knew in college was prepping for his mission, but his girlfriend doesn't want him to go. She wants him to stay and get married. He tells her he's committed to going on a mission. She gets preggers by some other guy and tells everyone its his. Stake Prez won't let him go until the baby is born and they can do a paternity test. Baby is born, and she's "shocked" to find that while she and my friend are blond with blue eyes, this child has dark skin, eyes and hair--which is as specific as I'll get here--not genetically impossible based on what I have said, but suffice it to say that it clearly wasn't his child. Stake Prez apologizes and he serves with honor. I lost touch with the guy, but he's bright and capable, and he doesn't carry that baggage with him. I am sure he's in good shape.
Bottom line in choosing a wife: Marry up. Make her settle. Of course, if you both feel like you married up, that's a really good match.