Do I need a bigger tampon?

I darted my period in October and have barley been able to fill a slender for most of my period but this time I am filling and leaking from regular witting 4 or 5 hours. No its no in wrong it's just a heavy flow. I have some super sized playtex sport tampons but I am only 13 I have never used on that big before and I a scared it wot come out or will be too full and hurt when it comes out or something, help asap!