Some advice please

I was with my children's father for 2 1/2 years and we split up shortly after we found out I was pregnant with our second child. He went on a drug bender till about 6 months ago where he decided that he wanted to come back into our lives. All of his words of saying he's trying to be there more for the children have just been complete lies and bullshit. He keeps wanting us to get back together but he is controlling and manipulative. I've tried telling him multiple times that we are not going to be together again and it's like what I'm saying doesn't even matter or like I never said it at all. I just want him to move on and accept the fact that after all he's done to me in the past will never make up for how he "tries" to be there for the children or me. How do I get this through his head? I'm tired of him continuously talking to me and never leaving me alone.