how do I break up with him ONCE AND FOR ALL!?

Hi all, this is my first time posting here :) I have been in a relationship with my boyfriend for 3 years now and I really want it to end. Although I love him to bits, deep down I know that he doesn't treat me right:( he calls me all sort of names such as whore, bitch, ugly, fat etc and also wants me dead :( he also confessed and told me that he doesn't love me or want me anymore. I have tried soooo many times trying to break up with him and always failed cause he can never take me serious! When I tell him that it's better to break up he just tells me "haha ok" , spends around 3-4 days without talking and then he always comes back to talk to me again. I'm sick and tired of this situation. I've tried blocking him on every social media and he still manages to find a way to come talk to me again. Also if I don't respond back, sometimes he will come to my school to speak to me. I really need some advice from you guys. 
Has anyone been in a similar situation? 
How can i break up with him and make him believe that this is for real this time? 
Thanks :)