How am I supposed to get through this when he’s the person I talk to about everything? I keep looking for reasons to yell at him because it’s comforting to talk to him but I don’t want to see him

He said they only kissed and he would pick her up and they would drive around but it’s been going on since we’ve been together. He swore on his dead father it was only kissing but that’s still cheating in my eyes. She also knew about me and didn’t care because “it didn’t effect her”