My boyfriend has been cheating on me for a while now with another girl and we just found out. Me and the other girl want to leave him speechless. What’s a good plan to break up with him?

I found out my boyfriend has been cheating on my with three other girls. He said that he didnt but i know that he did because thats what kind of person he is, but i love him and I try to pretend like everything is ok, I constantly lie to myself that things are good and are going to get better. I dont know what to do anymore the truth is killing me. Any advice?