I had the urge to read a private conversation of my classmate and I found out they were actually talking behind my back.
What did they say behind your back?
He said I was was retarded, but he's unaware that I know about their conversation.
It's understandable to be upset when someone talks behind your back, but its rude to read someone's private conversation without them knowing. If they find out you did this they will continue to make fun of you or worse.
He made fun of me and I know what he's saying behind my back. He's stupid and I'll beat him up now to show the world that people shouldn't make fun of others.
I understand you had reason to believe they were saying bad things about you. But that doesn't justify reading their private conversations.