It hurts beyond belief...it rips the rose tinted glasses off your face so rudely...so now, you look at him with clearer eyes and decide if you can like who he is now.
I don't know when your dday is but if it's fairly recent and you think you might like to R, spend some real time looking at him with those more piercing eyes. Don't decide quickly but really look. His actions (not his mouth) will tell you what you need to know.
My H, when asked how he could pretend that we were best friends etc...said that we are! He just thought I'd be stronger and okay with him having a girlfriend.
They make no real sense and honestly? Their poor behavior and choices have nothing much to do with us. As much as it hurts, he wasn't thinking of you at all.
You can be burned over that or you can take the little positive ray of light...he didn't do it because you did anything wrong.
It's all hard. I'm sorry.