The amount of discharge a girl produces varies throughout her cycle - you tend to produce a lot more during ovulation etc. So maybe have a look at the calendar and keep a tally of how bad it is etc and try and see if there's a link there?
Also, it could mean you have a yeast infection - which is nothing serious and can be easily treated. Signs of yeast infections: White, cottage cheese-like discharge, Swelling and pain around the vulva or Intense itching. If you aren't showing these symptoms then that's unlikely.
It is very unlikely to be any sort of infection or anything, every woman differs and it's actually a healthy things as it's cleaning you out. It is a pain though, and being a woman, I understand that. Perhaps if you are troubled by it you could go and see a nurse? It may sound embarrassing, but it's a common issue and at least then you wouldn't have to worry about it.
Hope this helps!