My man lying why do I try ?

This boy cody n I r technically going out just without the label. But everyone knew we were a thing. His family adores me n I found out the other day this fat ugly *** girl missi he works with slept over. I've been hearing stories of him cheating. I was with him last weekend and it was all good. Then today I went over because his step sister needed me. When I got their that missi girl wad there. He hasn't said a word too me. I asked his sister WTF was up bec just the day before we had " fun". Well his sister told me that their going out. WTF am I suppose to text him n say?