What should I do about him??

I am a young female teacher. There is a student at my school who is coming on to me very strong. He is not in my cl however, we know each other. I have talked to him about his advances, but he continues to tell me that he doesn't care what others think. He is 18 and I just turned 30 two weeks ago. I refuse to jeopardize my job...but he doesn't seem to want to take no for an answer.