Should I rid this Capricorn..

Here's my dilemma, people tell me if you want him to go away forever then just say so and he will, but I honestly don't want that. I still want to be his friend, typical Aquarius I suppose. I've taken the steps to "rid" him. Blocking him on social networks but he still finds a way through. Mind you I've known him for 5 years and we've been intimate a few times. The reason I've taken the steps are because in a way I feel used, but he's even admitted that I've "used" him for years and no not sexually. He says mentally, emotionally and I tortured him which I knew he was being honest because of the environment at the time. I have this sense of obligation towards him and I cannot escape that either, I did treat him terribly in high school, he liked me for a whole year and everyone would tell me, but I didn't really pay attention and now I'm here being lame.

So I don't want him to go away even though everyone says I should tell him to. What should I do? How to end the sense of obligation nonsense? Thank you