Desire, it sounds like you agreed to something you didn't really want and it was thrust upon you when you weren't ready. It sounds like your husband announced he had fallen in love with someone else, and just proceeded to continue the relationship without negotiating boundaries with you nor going at a pace with which you are comfortable. No wonder you went into it kicking and screaming.
You do have the right to say that poly is not something you want.
You have the right to ask that things slow down.
You have the right to expect that boundaries be respected and to follow through on the consequences if they are not.
What do YOU want?