Sorry you qualify for membership, but it's a good thing you found us.
Rule #1 is 'Take what makes sense; ignore the rest.' You'll get many opinions here; you get to choose which ones, if any, you'll adopt.
First, take care of yourself - lots of water, at least some non-junk food, physical movement. Sleep may be tough for a long time.
Understand that your brain will want to get away from the pain as quickly as possible, and your head will be filled with contradictory thoughts and feelings for some time. You're probably in shock.
You do not have to make big decisions now. You can give yourself time to figure out what you want and what is possible.
If you forgive too easily, your W will just have to deal with it, if you go into R (reconciliation) - and if she's committed to R, she'll deal with it fine.
I strongly recommend reading at least the BS FAQs in the Healing Library (link is in the yellow box at the upper left of SI pages).
Also, checkout the Just Found Out threads identified by 'bull's eyes' and 'beyond remorse and regret' in the R forum.
IMO, you've been inundated with too much emotion for your system to handle. Recovery for you is 1) processing the feelings (anger, fear, grief, shame) out of your body, and 2) resolving resistance to processing the feelings. I'm a big fan of IC, if you can find a good one.
I also think it's necessary for you to define some measurable/observable requirements for R, if that's what you choose. That way you and your W can know how you're doing and what areas need more attention.
IMO, one of your requirements needs to be IC for your W, with a goal of changing from cheater to good partner. Other requirements are No Contact (NC), honesty, and transparency (see Healing Library).
MC probably will be helpful at some point. IMO, a good MC can help immediately if the MC is good, but lots of SIers think MC should be delayed until IC has taken hold.
And you can add specifics that are meaningful to you. My W had to arrange dates for us, for example.
Understand that your W cheated because of her issues, not because of anything you did or didn't do. That's why she needs IC, IMO. (BTW that's one of the key indicators of a good MC - an MC who sees As as symptoms of problems in your WS may be a good MC. An MC who sees an A as a symptom of an M problem is just plain wrong, and probably close to useless.)
This site is called 'survivinginfidelity'. It's about that, of course, but it's also about thriving after infidelity. I urge you to take that as your goal. Thriving really is possible.
Before you decide to R, I urge you to consider D, too. R is difficult. I think it's a lot easier to deal with the difficulties if you know you have another good option. You may want to be with your W, but you don't need her.
ETA: I see SerJr has responded. I recommend as strongly as possible that you listen to him - his name is all over threads that helped me tremendously when I joined.
More important, recovery is a marathon, not a sprint. Life will suck for too long, but you'll probably start feeling better in 3-6 months, and you'll feel better and better as you heal - but the rule of thumb is 2-5 years for recovery.
So settle in, fasten your seatbelt, and have faith in yourself to get to the right destination for you. It'll just take longer than anyone wants.
[This message edited by sisoon at 12:55 PM, February 4th (Saturday)]