Welcome to SR. I"m glad you feel safe enough here to post your story, which all though not uncommon, is still YOUR story. It sounds like an affair all most, what she's been doing for so long behind your back. No wonder you're angry.
I can so relate to the anger. The trick is letting go of it and putting boundaries in place to keep you safe. The others will be along soon to welcome and help you. Glad you're here!