i had unprotected sex with my girlfriend on 4/14/12 and her last period was 4/5/12 so pretty much almost a week after her period.then she took a plan b pill 20 hours after we had sex. i dont really understand the whole ovulation thing so i hope somebody can help me. shes says shes been feeling like she has too vomit since like wensday but she hasnt vomited im hoping its the side effects of plan b im not sure but im freaking out.