Struggle -- Help!!!

Ok this follows on from my troubled story post.. So my ex gf nac and I called it quits les than 4-weeks ago. There a was long history of abuse as you will see from my earlier post. In true narc fashion she messages me two nights ago to say she wished things were different but she is now seeing someone and is happy. This was the guy she was seeing...

Now I have done a bad thing and looked at her fb and she has plastered photos of them on her profile (she never did that for us in the entire 18 months). I clicked on him and he put his relationship status to in a relationship with her on the 22 June.. We only broke up on the 13th of June... She was still texting and sending pics of herself asking for sex on the 15 th of June....

There has been a heap of bad stuff like this our whole relationship... Why am I in who know angd gutted...

Help me reason this!!! I know she has purposely not blocked me so I will see... This is just cruel