Ex Boyfriend

So my girlfriend invited her ex boyfriend to go to her house tomorrow, should I be mad, sad, scared, cautious? (Me and the ex boyfriend have a history of not getting along.. like.. at all. I need advice on what to do. I'm not dumping her. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^That was my last post. it is now the day after he came over to the house and the day was NOT fun, there were times where I was slightly okay with him but then he would do some things that would make me want to rip his head off. I asked her "This was just a one time thing right?" and she didn't give an answer at all she just gave me that fake "yeah " it's hard to explain over text but she sounded like she wanted him over AGAIN. WHAT DO I DO?!?!?!?!?