please don't have this come across as rude cause its not.

why does he bother you so much? what is it about him that just irks you so.
he is living his own life and doing things his own way, do you know the whole story about him, or only from what you have observed?

does he talk meanly to you? or act rude to you? if not i think you will be able to get through all this.

sometimes theres more to the story than what looks like is going on. have you sat down and talked to him about all he is doing? whats in his head?

you know how good you are and what your worth, you will be able to go on with your studies, cause it's you who you care about in achieving your goals, not him. don't let someone else dictate your feelings.

and who knows maybe he is staying cause he has NOTHING they might be giving him more time. if you REALLY need to know just ask him, can't hurt any?