Because you meant it when you said "I do." You care. And that's ok.
Work through the emotions. Everything you are describing is normal. And, I'm living the hurt, pain, anger, resentment cycle myself. And in the same house with stbxw. So, I know.
Recognize what you are feeling, let the emotions out, then get your focus back where it belongs - on YOU and your new future. I am doing this as well. I realized yesterday after getting some very good advice from a friend that I have allowed my focus turn back to my stbxw and whay she won'y work on the M, etc. My focus needs to be on me and moving forward. Focus on positive things and not the negatives from the past.