However, it mostly sounds like the period on March 18 was your official last period
before getting pregnant. For that date, here is what the conception calculator
First day of last menstrual period: March 18
Probable date of ovulation: April 1
Possible dates of conception: March 28 to April 5
Due date: December 23 (40 weeks)
According to the conception dates above, the two days beginning on the 26th would have been too early to be the legendary "implantation bleeding.