Period/weight loss question!?

okay im 13 5 foot and 107 lbs im also a level 9 gymnast and i train like 20 hours a week. im pretty muscular. ive had two periods and my third should come soon. im going on vacation in like 4 days and i cant have my period there. so about how much weight should i loose to stop my period?? how much do you have to weigh to have a period? thankss(: