Implantation bleeding typically occurs around 6-12 days after conception when the fertilized egg attaches to the uterine lining. It is usually lighter and shorter than a regular period. If you had implantation bleeding on May 1st, it is likely that you conceived around April 19th-25th. To determine how many weeks pregnant you are, count from the first day of your last menstrual period (LMP) and add approximately two weeks. Keep in mind that implantation bleeding can vary in timing and intensity for each individual, so it's best to consult with a healthcare provider for an accurate assessment of your pregnancy progress.