My girlfriend who has been taking birth control habitually everyday at the same time for the better part of 8 months is worried because she did not get her period. It was supposed to come Thursday evening or Friday. It is now Saturday afternoon. Tomorrow she starts her inactive pills. She just became sexually active about a month and a half or so ago. We did have sex 6 days before and I did not use a condom, however I never ejaculated into her. I know sperm is always present but I never climaxed in her. She is a student attending college and has a fair amount of stress and is in general a worrier. Should I be concerned ?