This is a very common discussion among both WS's and BS's. The general, collective wisdom on SI is to tell the whole truth, and I'll offer you my perspective on why that is.
First, let's clarify something so that we're on the same page. Infidelity, by its very definition, requires the WS to do some very unkind things. It involves lying. It involves hiding. It involves gas lighting, minimizing, and cover-ups. It involves living a double life. It involves selfishness and entitlement. And more than anything, it involves betrayal.
What it doesn't involve is truth, rationality, empathy, self-respect, dignity, or kindness. It robs the BS of their agency, of their choice. It even risks their health. Who knows? One of those men you were with may have had an STI. If you slept with him and then your husband, you may have passed that on to him, and he never even had a say in taking that risk. Or your AP's spouse may find out and come looking for your husband to take some revenge/payback on him. You just don't know. You've already put your husbands health and life in possible danger, and he's completely unaware of that fact.
Let me ask you this simple question. Are liars good people? I'm not talking about hiding a surprise party here. I mean lies that hurt people. Like infidelity. When you were a little girl and people asked what you wanted to be someday, did you say, "I want to be a liar and cheat on my husband, then hide it!" I don't think so. My guess is, whatever you wanted to be, you probably saw yourself as a good person, someone you are proud of being, someone with integrity, authenticity, dignity and respect.
Somewhere along the way, probably due to trauma in your life, what you never wanted to be... became who you are.
There is no unkind act in the world that is "made right" by preforming another unkind act. In other words, if you are a liar, you don't stop being a liar by lying about it more. If you commit a crime, commiting another crime doesn't make it better.
What many WS's do, both during the A and afterward, is come up with excuses and justifications that seem to make sense to them, but in reality, are really just a way to cover up their own bad deeds, and harm their spouses more. The most popular of these false narratives is the, "I did the bad thing, they didn't, so I should be the one to suffer, and they should live in ignorant bliss". We tell ourselves we are doing "the kind thing" by lying and hiding the facts and truth about our previous lying and hiding, and by removing all choice, trust, truth and safety from our spouses and choosing to control their lives, relationships and outcomes for them. Ones that always, conveniently, hide our lies and abuses from them. If I told you a story about another person who cheated on their spouse, lied to them, took health risks, and then hid it all, what would you think of them? Would you say, "Wow, what a prince! Sounds like a great person, I want to be just like them!" Or would you say, "Sounds like a real dirtbag to me"? Which are you? Would you rather be a liar and continue to be a liar, or be a liar who realized her mistakes and did her best to change her life and be a better person?
Does continuing to lie to your spouse sound loving?
Does taking hiding the truth and taking away their choice sound kind and empathetic?
Does making sure you never get caught sound like the responsible thing to do?
Do you go to bed at night feeling like a good person, knowing that you've successfully lied to your spouse and gotten away with abusing them and treating them like dirt?
Even if the affair(s) are 100% over and done, and even if you never have another affair, you are STILL, from the BS's point of view, having the affair, because you are still lying about it and covering it up. And let me tell you from experience, no one EVER feels loved and respected by having their spouse lie, cheat and dishonor them. Never. The abuse continues because the lies continue, because the coverup continues, because you have all the power here and he has none, no choice, no knowledge, and no ablity to make decisions for himself in his own life. It's all about YOU, the WS, and what's most convenient and least painful for you. That's not a personal attack, that's just how it is in a WS/BS relationship that is still underground.
Look, let's get one thing straight. For a moment, let's take your spouse out of the picture altogether, and let's instead focus on yourself. People who love themselves, who have healthy boundaries, self-respect, dignity, authenticity... don't have affairs. Not even because of what it would do to their spouse, but because that's simply NOT WHO THEY ARE. If I gave you a gun and asked you to go shoot a person (and promised you'd get away with it) would you do it? Why not? Well, for most people, it would be because they simply refuse to be that kind of person. They could never sleep at night having killed a person. They could never live with themselves having debased themselves and others in such a way. So... infidelity is no different. Yeah, you lied and cheated on your spouse. But before that ever even happened, you disrepected yourself first. You lied to yourself, and made excuses and justifications about why this would be okay to do. Think about yourself as a little girl again... if you could go back and time and tell that little girl what she grew up to be and what she did to herself and her spouse, would you be proud to do that? What do think she would think of her future self?
Please... please be the kind of person that little girl would be proud of. You can't undo what you did, but you make can make choices about who you will be today. You can own your mistakes and earn back your dignity, or you can continue to live a lie. Think of a person you really trust and respect, someone who you wish you could be more like... and then be more like them.
So my advice? Sit down, and tell your spouse EVERYTHING. No trickle truth, no "saving you more pain", no "you don't need to know that, it won't matter", and no "I admitted to one, that's the same as admitting to all of them". Tell him about each and every affair, how it started, what happened, how it ended, and how you felt about it. (When it comes to the intimacy, start by saying if it was an EA or PA, and then ask them how much detail they want about that). Here's a tip I'll share - the lies are 100x worse than the infidelity. By being 100% honest, you are starting down a path of rebuilding trust. More importantly however, for now, is helping your spouse to put together the pieces of what really happened. You know everything, they know nothing, and that's a terrifying and frustrating place to be in for them. Even though it is so very painful to hear about being cheated on, once heard, it's over, and that's a small relief. That is, unless lies still exist. And then every single time another bit of truth trickles out, the clock resets, the pain and the anger and the hurt and the humiliation resets as well, and the people here refer to that as "going back to square 0". It's WORSE than the affair because at this point, you are aware of the pain they are in and the damage done, and yet, if you choose to keep lying, then are you are still hurting them, and that's the most painful feeling in the world. It's evil. Don't do that to them. Don't do it to yourself.
I wish you luck. This whole thing is a shit-show, but there is reason to hope. I'm almost at year 8 now after d-day, and we're working through it. You can too. But if there is to be any hope at all (and even if there is no hope) it must start with honesty and accountability.