Originally Posted by Arisu
The two of them sort of decided on this without me present, started their relationship in one night, and I consented the next day, with reservations but optimism.
They didn't decide on a poly relationship. R cheated on you and then informed you. You, apparently, decided you'd go along with it, but I'm guessing so you wouldn't risk losing her?
You're feeling bowled over because you have been.
I think way too many people use their 'issues' as a way to tell other people what they must do, however, your abandonment issues have nothing to do with this. R and S are behaving thoughtlessly. They've rushed into things and really just informed you this is the way it is, from the sounds of it. It sounds very disrespectful.