I think a local DB support group would be good, except for one thing....it's a broken hearts club. When you talk a member of the opposite sex about your marriage problems, you are saying I'm vulnerable, and subconciously, you are saying, I'm available. It might be a breeding ground for revenge affairs. It might work if they were single-sex DB support teams.
Luckily 99% of my friends want our marriage to work out. It's my wife who is starting to lean on friends who don't have a loyalty to our marriage and who will support her "unconditionally", even if she has an affair and divorces me. Don't know what to say about your situation.. Find a good church where they support marriage. Some more liberal ones will support whatever decisions you make, and won't help you stand for your marriage. If you want suggestions, I can email you a few links.
View this time as an opportunity to find what brings laughter and joy. How about old hobbies/interests? It took me almost a month to write down what would interest me. But I did and got to it.