3 days delayed period, is it bad?

My period is delayed by 3 days. I know it ain't much but I'm just concerned. I just came back from a 2 week vacation from Mexico a week ago and lost 5 pounds can that be affecting my period cycle? I haven't had any . So there is no way I'm pregnant. And I'm going to El Salvador in 4 days. So any ideas why i'm delayed?