Need Help! Am I being selfish? Should I call him??

I broke up with my ex 4 months ago and it's been a rocky road since. I ended it because, although I gave him many chances, he continued to lie to me and cheat with his ex. He's apologized and begged me to give him another chance, but still denies cheating even though I have IMs and myspace messages that show him cybering with some girl, plus I know he spent A LOT of time with his ex, including a weekend getaway, which he first lied about and said she was a guy friend, but after I found proof, he made some crazy excuse and said nothing happened. After I refused to talk to him or give him yet another chance, he started spying on me, stalking me online, insulting me and even had his friends attack me. Its been hell, yet he continues to tell me he loves me and can't live without me. I absolutely do not want him back and I've told him so, I've finally come to recognize what a toxic man he is. However, I've been talking to him thru email and occasionally on IMs because it seems to keep him from torturing me like he did when we first broke up. But no matter how many times I explain why we will never work, he continues to bring up getting back together. I told him it would be better if we didn't talk anymore because it seems to be preventing him from moving on but he gets all upset and begs me not to.