Is there a pill to stop a period once ur on?

i know its a bit tooo late but i thought i wud of bin n gon by now but i think i will start tomoz n i gotta go in hospital for two weeks on tues..embarringggg. i know there is a pill to delay it, u need to take thar two weeks prior. but me m8 said she's sure theres one that will stop it once started, she cant member anytink else about it. numpty, hee. cheers in advance. x