Welcome to HCM,
bleeding generally occurs within one week prior to due date of period.
It is very light/spotty, light pink or brownish in color, which can occur for few hours only.
If blood spot is bright red in color, it can be due to period and in that case within short period it will become heavy and continue for usual duration.
Thus if spotting doesn't follow usual period within a week, do pregnancy
test at your home.
And if it is +ve, contact your Gynecologist.
Please avoid unprotected sex in future to protect yourself from STDs.
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Hope you found my response to your query informative and helpful.
With good wishes,
Dr.Chandra Shekhar Sharma