Secondary amenorrhea cause

Hi,
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Sperms do not live in dry condition. If semen or pre-cum (lubrication fluid) is left dry for about 20 minutes, they usually die. They need moisture to stay alive. If freshly ejaculated semen or pre-cum has come in contact with vagina, then chances of sperms being alive is for about next 2-3 days (inside female reproductive tract). If you were in your fertile period (time of egg release from ovary) or close to it at that time, then delay in periods could be due to pregnancy.
If there was no contact with semen or pre-cum, then the delay could be either related to your medication use, or anovulation (no egg release from ovary in this cycle). If you have been regular periods before this time, then this delay is abnormal. Visit your gynecologist (not regular doctor/GP) for examination and further tests to look for underlying cause for your absent periods (secondary amenorrhea).
Take care.