How do I say no?

the best way is just tell him the truth..no im not interested in you what so ever go on with your life...if that doesn't work get a restraining order out on him..it's hard but be live me after he finds someone else he will forget about you..I have been in this situation and it worked after 2 yrs of being hared by him now his married and yes he calls but he knows we are over and never crosses the line...Good Luck...