What's Going On Here?

I'm almost 12 and for a while, I've been having vaginal discharge, but it was only a really small amount every once in a while. But now, it comes everyday in huge amounts. And it gets really annoying. My mom bought me those pantyliner things and they make everything worse because you feel like you're wearing a huge, wet diaper. But, when I don't wear them, the discharge gets in my underwear and makes it also uncomfortable. Is it normal to have a lot of discharge and should I be worried about it? And the weird thing is, I never have discharge when I'm exercising, it only happens when I'm just regularly walking. And it never happens at home either, just at school. Which makes it even worse because I have to walk like I'm retarded or something because my underwear's wet. I put up with it for a while but now I'm done. It's so ridiculous.