Im confused on how the doctor decided on my due date. I had my period Feb 15 tell like the 20th. And the 27th was the last time I had intercoarse unprotected. And on March 5ish 6th. I spotted. It was nothing like period blood, it was like pinkish and I could only tell cause there either be a tad on my under wear or on the toilet paper after i wiped. But I had sex that night and my Bf thought I was on my period since it got on the condom. But I had my period two weeks before that. And Im pregant, and I thought Dr's went by the first day of your last period to determine your Due date, but my due date goes by the day I spotted. Is that right?