Hi JamesL, glad you found this place. Sucks to be here, but this really is the best place to be for what you're looking for.
I want to say that my exWW (ex-Wayward Wife) did the exact same thing at the exact same age with the exact same age AP (affair partner). Kids the same age as your daughter. Let me guess: the AP works with her, too?
Can you tell us a little more about the background? How did you find out? Where are you living now relative to WW? What is your parenting schedule like?
Big ones: have either of you filed for divorce? Is the AP married, and have you exposed to OBS (the other betrayed spouse)? If they work together, did you expose to work?
These things can help kill an affair. However, from what you've described here, it sounds like they're already living openly as boyfriend and girlfriend. Is that right?
~
Regarding healing and moving on, I'll assume you're headed toward divorce.
To start: read everything in the Healing Library on the left. Everything that applies to you.
Second: keep posting here. Talk it out. There is a lot of collective wisdom here.
Third: here's a list of stuff in no particular order:
-- stop checking her social media, ever
-- start exercising. Get exercise every day.
-- do things that make you feel confident, like getting new clothes, a new haircut, growing a beard, shaving a beard, getting new cologne, etc.
-- get a stupid game on your phone and play that
-- get into your hobbies. Pick up an old one or start a new one.
-- focus on your kid. She's awesome and the true love of your life. Embrace that.
-- Recognize that stable, single dads with dad bods are actually pretty sexy out there in the thirty- and forty-something dating markets. Seriously. Just think about that, and maybe just envision a future where there are other women interested in you. Because there are!
~
That's all just a start. Again, give us a little more context and maybe we can give better advice.
FYI, I was exactly where you are now about three years ago. This divorce has been one of the best things that has ever happened to me in my life, and when I see exWW now, I can hardly believe I was ever connected or even attracted to this woman. And I was absolutely head-over-heals in love.
Hard to see now, but there is likely a big breath of fresh air in your future.