I am a young teacher at college. I have to go way too long, I know but I have the following problem. 

In one of my classes, I have this guy who pecks at me for everything I say.. he is conceited sure to say, but it hurts like hell when he makes fun of me in front of the whole class. 

However, I take no note of it in class, but later I feel very sad. This makes me frightened to go that class at all. 

He is overconfident and imposing and seems to have got a big gang behind him. He is a threat and he disturbs me. Please help me tackle this situation.