Getting my period to come earlier this month Watch
I doubt you can bring on a period like that, but they can most likely give you a pill to delay, (how much would depend on your cycle. i guess).
It really can't be good to go screwing up all your natural body cycles...
There is a medicine that can delay your period and isn't a contraceptive (so your mum won't freak out when she finds you're on it). Would that be OK? You need to get that from your GP.