Hi.. I Go On Holiday This Friday And Got Norethisterone

Hi.. i go on holiday this friday and got norethisterone prescribed as i thought my periods were due thursday. I had slight bleeding monday so thought my periods were coming so thought i would let them run their course as they usually only run 4-5 days and would be fine for my holiday. But i never got bleeding during last night of this morning so started taking the tablet hoping it would work.. but as iv taking it today iv had bleeding as though my periods are now coming.. if i carry on taking the tablet will it stop my periods? Or if i stop tablet after only taking it one day will periods just carry on and not be affected? As if this is my periods starting im happy to let them too. Thanks