{A/n: Ik there is alot of repittion in this, but like yea..}

Stan: The person he cheated on you with told you

Kyle: He felt bad so he told you

Eric: Someone found out and told you

Kenny: You caught him

Craig: You caught him

Tweek: You caught him

Token: He told you

Clyde: The person he cheated on you with bragged about it to you

Jimmy: He told you

Butters: He wouldn't cheat but if he did then he probably would have told you