It's a high dose of hormones into your body, similar to overdosing on BC (which is basically what it is) It can cause any 'symptoms' similar to those of pregnancy. However Plan B
isn't an all safe thing you can use. It doesn't cover multiple episodes, just the most recent. It works to prevent ovulation, or if that has occurred with fertilization, to keep the egg from implanting. It's a very foolish gamble to take, especially if you're not looking to be pregnant.