Don't be so afraid of it... Sometimes periods are late, it may be due to stress, tension or hormonal changes... So the best would be to see a few days and then find a doctor. Read here:
https://lovematters.in/hi/resource/menstrual-cycle
https://lovematters.in/hi/our-bodies/my-periods-are-irregular-what-should-i-do
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Don't be so afraid of it... …