There's no easy way to break up. In my opinion you should make some kind of a preparation conversation. I'm not familiar with the dynamics between you two, but I guess that discussing about your feelings, and the problems as you see them in your relationship will be good enough. You might want to consider writing a letter, Some times it's much easier to express complex feelings that way. Try also to be assertive, don't let him try to manipulate you that way or another.

Good luck .