Is it too late to start brushing again?

I'm 12 and I don't brush my teeth all the time. But I do sometimes. So my teeth are stained I've had 3 cavities in my life. I'm afraid my teeth are ruined forever and I'll get a serious teeth disease or something. I'm so scared is it to late to start brushing again and say my teeth?

Of course not. It's never too late.