Can u speed up periods?

Kathleen
Ok so on eve it says my period (started this morning) should last 5 days. But this Friday I'm going to a pool party. Usually my periods don't last the full 5 days more like 3 or 4. But I've never used a tampon and really don't want to but I still want to go swimming around 12 or later this Friday. Anybody know some helpful ways to speed up the process?