I'm a bully in school and no one knows
Who did you bully?
I bullied everyone around me for years
You are wrong to bully people at school. Instead of bullying people you should be kind to them.
If everyone else doesn't know about it then I'm not a bully.
You are still a bully even if everyone is clueless about your bullying. You still are hurting people by asserting power over them which makes you a bully. You need to stop before someone hurts themself.