Annoying ex, keeps winding me up?

Well dear, I think this is happening because you are allowing him to get to you, maybe try speaking with him alone, and tell him you dont appreciate him telling lies about you, and spreading stupid rumours over the school. Of course he will deny it. Then I would strike when he thinks he is so full of himself, and say to him, look, I didnt want to say this, but being that your not prepared to be an adult about this, I want you to know that you were the worst boyfriend that I have ever had, you were not good at anything, and I dont even know why I wasted my time on you. Now the last bit, I dont know whether you were having sex with him, but the best line if you were, you can say, hey and dont flatter yourself about the sex, you needto go and get some lessons somewhere because you have no idea of how to please a woman, then walk away and leave it at that. Then if you see him anywhere, make sure you are always with other guys, you know act a little just to show him you can do the same and can get others in your life, look at him and laugh loud enough, he will shrink, trust me, big blowhearts lilke him need to be brought down to size. Then hold your head up high, you are woman, we can conquer anything, go girl, teach him a lesson or two. Good Luck