Everyone in my life says the same thing: "it was so long ago, she was young (early 20s at the time), you weren't married, you need to forgive and forget".
That's bullshit. No matter when your wife actually had the sex, to you it occurred when you found out about it.
Further, there is the fact that she lied about it for 12 years, and she clearly did it intentionally because she was worried you'd leave her if you'd found out a long time ago. In a very real sense, your relationship is built on a lie.
Who is "everyone", by the way? Does "everyone" include any person who knew of the fucking -- or, heaven forbid, the one who walked in on them fucking at the party -- and failed to tell you about it back in the day. If there is any such person in your social circle, that person is total scum, an enemy of your marriage, and should no longer count among your group of friends (nor your WW's friends).
It just doesn't feel that simple to me. I feel like my life has been stolen from me, that we married under false pretenses and have kids that are the product of a lie. I question who I am as a person, as a husband, as a dad. I don't want to spend my life with someone who could do that to me. I want to be loved the way that I love her.
Your feelings are 100% normal. It is probably wise to not make any decisions right away, though. The first step is to try to get your balance. Take a deep breath. Hydrate. Try to avoid alcohol and exercise as much as you are able.
Next step is to go to The Healing Library (Yellow Box top left of this page). Read about the 180. The purpose of the 180 is to create some psychic space for yourself, some "breathing room" to center yourself. Your task is to find your heart's truth. It is not easy in the beginning because you will find yourself in an emotional roller coaster, alternately hating her, loving her, loathing her, longing for her.
Also, find "Joseph's Letter" there, print it and give it to her to read. And get a copy of "How to Help Your Spouse Heal from Your Affair" by Linda MacDonald and have her read that (you should read it too).
All that said, I do love my life, I love my kids, and up until I found out about this I loved my wife. I think I still love my wife. I am just so mad, and so hurt, and it goes against all my principals and beliefs to forgive her.
That is normal. Take your time finding your heart's truth.
There is the lie, but there is also probably a lot of truth in your relationship. These circumstances aren't black and white.
Am I crazy for thinking of ending our marriage over this? I don't even really want to do it, I just feel like I have to. How can I stop feeling this way and make it work? My wife 100% wants to make it work and says she only confessed because she thought our marriage was in such a good place that I could handle it. She had no idea how much pain it would cause me.
You are not crazy, not in the least. There are threads here on SI where a betrayed husband (BH) divorces his wayward wife (WW) because of a drunken ONS, or even an online fantasy A where no physical contact occurred at all. There are threads where the BH successfully R's (reconciled) with his WW after the most horrific and flagrant LTA (long term affair), including delivering sloppy seconds to the BH, etc. There is no "right answer" other than your heart's truth.
A very large factor is the degree to which your WW has empathy for you, and uses that empathy to find true remorse that she uses to help you heal from the trauma. The heart knows what it knows.
Another factor will be your ability to trust whether she is telling you the full truth. It is very common for cheaters to minimize the extent of their cheating, even if confessing. Things that are legitimate that you should at least consider:
Get STD tests for both of you. I realize this was long ago, and it is possible you got STD tests for your marriage license, but some STD's can be latent for quite a long time and, further, if she is minimizing and there was other cheating, you could be at risk.
Get your kids DNA tested to be sure they are your kids.
You might also consider putting a voice-activated recorder surreptitiously in her car. There are techniques to this that you can read about here on SI. In the turmoil that will be taking place in your marriage, it is likely she will be talking about this with her friends. Nowadays, a lot of this takes place in the car, while driving. At the very least you will get a good understanding of where her heart lies if you can listen to these conversations.
[This message edited by Butforthegrace at 2:10 PM, November 1st (Thursday)]