I had just finished my placebo week and had started a new pack Mononessa birth control. I had accidentally forgotten to take the SECOND pill of the first week - which is the most important to take on time and on schedule. I had unexpected and unprotected sex later that week, before 7 days had gone by so I wasn't fully protected. I knew that I had just been without hormones for a week and had skipped a dose, so within the 72 hour period, I took Plan B: One Step. My questions now are - What are the chances of pregnancy? and When should I expected to receive my period, will it still come during the placebo week as usual? (I am 21, five feet tall and weigh about 100lbs so I know Plan B would technically "work" for me.)