He will not leave you alone just to respect your wishes. You are asking him to make it easier for you. He won't do that. He likes the set up, as it is, and he's not going to walk away from it voluntarily. Don't plead with him to understand how this is hurting you. That just convinces him of how much you adore him, and that makes it harder for him to walk away.

You'll have to do the hard work of not taking the calls or answering the doorbell, when you know it is him. Maybe you don't have the strength for that. If not, then you'll keep this thing going, until he gets bored with you. That might take a while because you are young and at the peak of your attractiveness. You might even keep doing this for a few years. Eventually, it will end. Then you will be older and having a harder time attracting the kind of guy you would really like to have.

The older you get, the less guys there will be who are single in your age group. Out of loneliness, you may end up doing what you do best - offering yourself to married men. You may end up going from one married guy to another. That's a terribly sad way to live. As it is, you are going to have to accept a certain amount of pain. Take the pain now. Later, it will only be worse.