WHY did he dump me??

I started dating this guy, so naturally, I stopped trying to impress people because what’s the point? I already have a boyfriend!!! So I didn’t brush my teeth or my hair. I stopped washing my hair, putting on deodorant, and dressed in my pajamas to school. But I guess I started to smell cuz everyone stopped talking to me. Then my boyfriend told me I was gross and left me. What did I do wrong????/