text: There is always a chance of becoming pregnant when having sexual intercourse. However, then chance isnt as high as people belive. If a woman has unprotected sex, at the time she is ovualting, she only has about a 25-33% chance of becoming pregnant.\n\nThe 'period' that you could have been experiencing could be implantation bleeding. This is when the fertilized egg implants in the lining of the uterus. This can cause spotting anywhere from 6-15 days after conception, and teh spotting can last anywhere from 1 day to 1 week.\n\nIf anything, at least take a pregnancy test. Urine pregnancy tests can determine a positive pregnancy 12-15 days from conception. A blood pregnancy test can determine a pregnancy 6-8 days from conception.