Watching step-Mommy peeing you can't help but get aroused. She doesn't notice you stood there in the crack of the door. She's oblivious when you watch her stroking her pussy after peeing. You weren't planning to push through the door as she pulled up her knickers. You didn't intend to get so rough with her, pushing yourself inside her, fighting her, using her. Your little brain just took over and in turn you took over her.