Why have i been on for so long?

im fourteen, and i have been on my period for about 2 weeks, maybe longer, and its starting to annoy me.its neva happened before, i used to be on my period for about 2-3 days, now its takin the piss lol. i dont really speak to my mum about things like this, so its hard to bring it up haha. ive been on my period since last september|-)