My periods slightly fluctuate for 3 days or so. Sometimes 3 days before or sometimes after. Date used to be 29, 30..my body weight is 59.I was never on such kind of pills before. I only take meftalspasm for the extreme pain during my period days. As I am off for the great himalayan trek for 15 days, I don't want my periods to come in between which will spoil my health as everyday there will be 7 to 10 kilometers walking and no proper water facility.it's there any other medicine to suggest