If you are in the USA, get a restraining order and USE it if he comes anywhere near you.
Oh girl, don't you know that as women we have no right to walk away from our abusers until they give us permission to do so. Geez. I thought everyone knew that by now.
I went through this just this past June. My ex actually came to my house and put his hands with me. I just could never get over the fact that the man I loved wanted to hurt me.I didnt want to call the police because his father is an officer. I called a friend that i hadnt talked to for a long time . He came in a heart beat. I felt safer with him around.
The only thing that will work is staying away from him and having no contact what so ever. Don't even look at him. Read the book called "The Gift of Fear" by Gavin de Becker. It gives alot of insight into his type of predator behavior. If you do what i said above within about 6 months he will get tired of his irrational obsession and move on to the next one. It takes about that long though for it to be affective. Note: Pieces of paper (restraining orders) mean absolutely nothing to these types of people.
what exactly does he do? if he is stalking or threatening you, and you have told him point blank to leave you alone, it might be time to involve the police. before you do that, though, think it through & be sure you haven't sent him any mixed signals.
he will stop as time goes by and if you give in than he would never stop doing it all over again