Period end- advice pls

Right so my period gets heavier suddenly sometimes when I’m stood up for a long time (e.g stood up all day shopping made my period heavy).

But anyway it’s the last day of my period and i was stood up for a while and I bled a little bit (even tho I’m supposed to finish today...it was a lil bit brown tho).

So idk when to tell my period has stopped bc it stopped this morning but then I started again and now I’ve stopped again. Idk what to do because I have sport tomorrow so idk whether to wear a pad or a pantyliner?

How do you guys tell when your period is over? Advice pls (don’t want the same thing to happen again half way through my sport lesson lol)!!!