Welcome to SI. SI can serve as a wonderful source of support for you. I haven't personally found any good local groups that address infidelity, however some of our members have gone to Sex Addicts Anonymous, and often there are church groups and such, if you are religious. Hopefully some of our other members have more resources for you.
That being said, I'd like to suggest the following. First, a book called "How to help your spouse heal from your affair" by Linda MacDonald. Also, "Not just friends" is a great resource. Finally, "The Healing Library" (see link at the top of this page) is a wonderful place to start. I suggest you read both the WS and BS articles, as it will help to give you some insight into the BS perspective and experience.
Can you share some of your story with us? It would be easier to help tailor some resources and advice if we had a little more to go on?
In the meantime, please, if there is anything at all that you haven't disclosed to her... do so. "Trickle truth" kills reconciliation efforts, and many WS's tend to hide behind a shield of "not wanting to cause them more pain" and so continuing to lie. This robs our spouses of their agency however. Reconciliation is all about rebuilding trust, and creating a new relationship post-infidelity. Truth and communication are key.
Please keep coming back and let us know how things are going for you.
Me: WS
BS: ISurvivedSoFar
D-Day Nov '16
Status: Reconciling
"I am floored by the amount of grace and love she has shown me in choosing to stay and fight for our marriage. I took everything from her, and yet she chose to forgive me."