I had sex on March 17th and sperm came in contact with the outside of my vaginal area. I've been on birth control for 3 years and never miss a pill but I was still a little worried so I took a plan b pill about 12 hours after. My period was due March 18th but it still hasn't came yet. It's been a week and a day now. There's really no way I'm pregnant but wasn't sure if I should be worried. Is this normal?