Yeah, KG and Arrow are right.
If your ex won`t stop bugging you and can`t take a no, you might need to be a little harsh.
He needs to accept that it`s over, so if you`ve tried convincing him in a less harsh way, you`ll need to try the other way.
I liked KG`s suggestion of going to a public place and try to 'finish it' there.
If you think the reason he`s doing this to you is just because he`s immature, (which is usually the case) be sure to act very grown-up and mature when you talk to him.
Saying things like "I hope you`ll be able to find someone else" and "I`m sorry, but it`s the way I feel."
Maybe then he`ll realise how serious you are about the whole situation.
Best of luck!