HAL123, BS 24+years post DD.
This whole thing is still new to you, and I will say you have a long way to go.
First, how do you feel now post DD vs. less than a month ago when everything was fine. To see your world and the world of your immediate family has been blown up.
From the beginning, do you think it was by chance that his brother happen to catch inappropriate behavior between you and OM. I believe everyone knew at the gym. I suspect your Brother-in-law was told, and checked it out for himself before notifying your H. Your H then had to find out the hard way.
I give him (your husband) credit he knocked you off the fence of the A real fast, which is why you are in the deep regret phase. Your anguish is just beginning; this will be a long hard road.
You are not alone in you initial "confusion", my WW did not fathom the depth of emotional murder she had created either. That happens much later. The waywards never understand the immense horror created.
They mention the rollercoaster, and that is just what it is. He has not hit the anger phase yet; which is why the truth will be very important.
Did you have unprotected sex? When you said you're husband ensured you were satisfied in other ways, did that include oral? You don't have to answer that here, but just in case be prepared.
The questions from your H will eventually come. If yes to unprotected sex with OM, and your H performed oral during the A, work on now your answers he will see the lies by omission or minimizing. Be prepared to tactfully give your answers.
To give you an idea on the stage he is in: Imagine someone you trust walks up and slaps you in the face. For the first second, you will be in shock. At that moment if they ask you if you are OK? You don't say anything. Therefore the slap was not so bad.
In 30seconds when you recover from the initial strike, you become angry and maybe try to attack them.
Timelessloss described the phases of PTSD, your husband is in the Shock Phase "Just been slapped", beware of reading into anything that everything is well, it's not. He will move into many phases, and anger brought on by triggers real or imagined will start.
Your two sons will also need counseling. There perception of female relationships has been altered. Did they respect their father? Then they watch how his best did not stop his wife their mother from seeking another. This will impact their choice in future mates for themselves. If dad did his best and his marriage failed, I will do the opposite of what he did. Both sons are watching how this marriage now plays out.
Go back and read your response in the mirror and watch how you respond. It showed a lot on how you attacked in the beginning. Your husband will see this also in your answers to him, be mindful.
I know you don't believe me, but you are not close to remorse, too early.
So why did you do it, I call it "Chasing the ghost" It's when you hit your prime and come to realize you missed out on your prime fun years. It's bullshit, life is what you make of it. It's your perceived "Ghost" image of life you didn't get. My best friend did it, and is probably still doing it. He got his girlfriend pregnant at 18y, could not stop partying and cheating. It oost him his marriage, and he never stopped.
You got lucky, you got caught and your H blindsided you. Only YOU can fix this no one else. It will take years for it to diminish for him; he will never, ever forget.
Be aware of paradox phases:
"It was just sex." This makes the BS feel worthless, because the A that destroyed his world was trivial sex. He rather of heard the OM was your "Sole Mate" than he was nothing at all.
"I Love You" or "I always loved you while the affair was going on" -- This phrase is seen as an automatic lie. How can you say that when you chose to be with another.
"The Affair did not mean anything" -- See "It was only Sex".
Same for the OM did not mean anything or I never loved the OM.
All of these phrases is just a dagger to the heart, and trivializes you marriage to him.
You need to really look at yourself, and be careful, you are on dangerous ground "thin ice", he will see through the false answers, and don't ever say something that you think is what he wants to hear, tell him the truth.
He will decide if you are both still together, not you. You now have to relinquish that idea. Only actions mean anything, your words have very little impact.