I had sex July 6th and took plan b. Then the week after I had sex again. The following week I started bleeding even tho my period wasn't due for another 2 weeks. Then when it was actually supposed to come it arrived 4 days late. I thought I was pregnant but since my period arrived I can't be pregnant right? I've been cramping all week but I can't tell if it's me causing stress on myself of its the period. Once you get your period it means you aren't pregnant correct?