Is there anyway to know if someone is torrenting in my network?

I live in a dorm. In a past few days, everything is fine until 7PM when I'm suddenly lag. And this lag goes on until around midnight. I'm suspicious that someone is pulling all internet signal, probably by torrenting.

So is there anyway I can find out who's torrenting from my computer? Or at least, anyway to confirm that I'm lag because someone else is torrenting?