My friends' period is 19 days delayed. She normally have irregular periods delaying between 5 to 15 days. It's getting too delayed this time which is worrying her. She had protected(condom-checked not broken) sex in last month after last period. I read somewhere that stress and vacations can cause it. She had 2 air tours in last month, 4 days each. Should she worry or should she wait? She felt like it's coming on 17th-18th day and she feels it will come in a week. Please advice.