How do i stop this Pain In My Heart, Can't Get over Him?

Things will move on. Things will assume a perspective. Meet new people, do things, learn things, see things. You will move on. You may never forget him, but that's ok. One day you'll meet somebody else. And maybe somebody else after that. And so on. And as you see more of life, you'll find it easier to choose which relationships you want, and which you don't. Including ones that are in your head.