Spreading rumours!

So I had all this horny chat saved with a guy in snapchat and he saved it and he unsaved his bit and only left mine saved. He is know for a bit of a bully but is one of those popular guys but he screen shotted my part and has said he is going to expose me to everyone. I have tried reasoning with him and what ever I do he wont stop. I know that he will be sending it around right now. It is in detail of what we would do to each other and it isn't anything embarrassing as such but he knows some other embarrassing things about me and I know he will say them too. Does anyone know what to do I'm still in high school. No hate xox