Welcome to HCM,
If white discharge is light and not foul smelling, seems to be normal.
Menstrual period start on 14th day of ovulation.
As ovulation has occurred on 3rd Aug, your period will be due on 17th Aug.
Bleeding due to implantation
generally occurs within one week prior to due date of period.
As you had sex on the day of ovulation also, your present spotting seems to be due to implantation.
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Hope you found my response to your query informative and helpful.
With good wishes,
Dr.Chandra Shekhar Sharma