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The delay in your periods could be due to pregnancy (since your unprotected intercourse was around the time of your probable fertile periods or time of egg release form ovary). The withdrawal method is also associated with high failure rates, so again chances of pregnancy cannot be ruled out.
Another possibility is due to late start of birth control pills. Once you stop the pills you will get your periods. However if you are already pregnant, then the pills will affect the babyâs growth and development.
Consider meeting your gynecologist for examination and tests to confirm/rule out pregnancy. If found to be pregnant, then stop taking the pills immediately.
Take care.