I think I misunderstood your comment "OP must know whether ow knew about her or not" - I took it to mean, 'OP must find out this information'. Sorry about that.
But I still disagree with throwing a comment at someone and immediately blocking them from responding. Even when that person has hurt you deeply. I really do think it is equivalent to yelling from a speeding car.
I can't help but feel there's even something a bit cowardly about it; what, you haven't got enough courage in your convictions to think you can defend them if they challenge you? Even if you let them rant back and just ignore it, that shows you're choosing to make them irrelevant. Which is what I think betrayed spouses must try to do. Far easier said than done, of course. But it's what I think they need to work towards, because otherwise you find yourself in a situation where, three years on, you're still being eaten up because something nice has happened to the OW and you can't rest...
I agree with Mags when she said, "It's not that I don't sympathise but if your choices are making you so miserable that someone else's pregnancy is causing all this years later, then maybe they're not very good choices!"
No matter how badly you were wronged, and some people are hugely, devastatingly wronged, once it's happened the only thing that matters is you and making yourself well again. And staying hung up on someone who isn't married to you, being upset for years every time something nice happens to them...what sort of a life is that?
Work towards one where the silly cow has no power over you!