Boyfriend cheated and somehow turned it around on me?

[Anna]

My boyfriend wanted to take a break. He said he wanted to clear his head and he wasn't going to hook up with anyone. Last night I found out he went home with a girl he had followed on twitter/Instagram the week before. He was sending my texts while next to her saying he never wanted a relationship and that I meant nothing to him. We hung out every single weekend. Went on dates.
Etc. should I even respond? I think he's honestly insane. I don't even know what to say to any of it. He was so manipulative and I was completely blind sided by all of this.