I'd not make it as fixed as Starsky suggests -- (1) you can't know how you will feel in the future (2) I have NEVER seen a case where contact ends cleanly or neatly. It takes time to get back to a monogomy.
But, I agree strongly that you need a boundary. Of course, YOU were also in contact with OW and YOU plan to see her in June.
So, you BOTH have a bit of work to do to get back to a monogomous R with transparency and no contact.
BTW, I'd wager big money that (1) W called OM and (2) she did it to self-medicate because of the deep pain and hurt caused by your disclosure about OW. After all, who is she supposed to go to that pain with, given you were "fully justified" in getting sexually and romantically involved with OWs. Neither of you left space for her to come to you with that pain.
So, rather than ultimatums, judgments, and an air of moral superiority, you might better substitute:
"W, it really hurts me that you were in contact with OM. It feels good that you were honest about it. If we are going to give this M its best chance to become a fulfilling, vibrant, passionate M that works for both of us, we both need to commit to no contact with anyone who is not good for our M. That means my OWs and your OM. We have to work together to rebuild trust on both sides -- this requires a clear commitment to no contact that has been transparently communicated to the OWs and OM, continued transparency, continued no contact. If we are going to try this together, let's do it right. Neither of us knows how things will work out. We won't be bad guys if we later choose a different path. But now we need the safe space and time to see where we land, hopefully in a good place. I love you. You must have been in a painful place to renew contact with OM. I'm sorry for your pain. Let's share it and be here for each other. You are worth the emotional risk to me. I am sorry if I caused you pain because of my Rs with the OWs. It doesn't matter that we were separated. What matters is that we can share our pain, empathize, forgive, and heal. I want us to feel safe with each other, open, and honest. Clear air, bright future."
