Lisp help. please help!!!!!?

Hi I have a lisp and I am 14 years old. I find it really embarring and i hate to talk now, I find this horrible as I am outspoken and really jolly. I went to my doctors regarding my lisp and he advised to go to school nurse (My school don't have school nurse) but he insists we do! Anyway he said to speak to school teachers but I am embarred but I do want it to go as other kids tease me what should I do? Please help 10 points to best answer!! Thanks