Hello mate, I don't know whether you know my history or if you've ever seen any of the problems I had with my ex, but I know how you feel.
At the end of the day, you can spend hours trying to work out how to make the marriage better, how to punish your ex for what she's done, how to make sure this never happens agai; but it's all pointless unless you've got your own head squared away.
You have had your pride, confidence and trust shattered. You're probably questioning every little thing thats ever happened in your marriage before (every time she's finished work quite late, every girly night out, etc). It's all normal. And if you're anything like I was, then you're in absolute Fluffing pieces right now. Eating, drinking, sleeping, all of this seems irrelevant.
Trust me, it's not. You have to get yourself back on an even keel before you make any decisions about anything. You probably want to scream, shout and lash out at anything that gets in your way; and who can blame you.
My advice to you mate is get yourself away, whether it be going to stay with a brother for a few days, or getting a tent and driving up to the lake district for a couple of days of solitude, fresh air and exercise.
Let yourself cry like a baby, and when then anger boils up again, work it out through exercise. You said earlier that you go to the gym, so get down there and pound ten bells of Sugar out of the punchbag, get on the free weights and bench-press till your arms want to drop off, get on the runner and go hell-for-leather until you want to puke.
Let those magical, wonderful endorphins do their job, and let the stress sweat out of you.
As for Vibes suggestion about baring your teeth, I totally agree. When all is said and done, we males are a primitive tribe, and sometimes going a bit primative on someone can be incrediably theraputic. I'm not talking about knocking him into next week, but just warning him that the next