"i took plan b one step 7 days ago (sunday). i was days before ovulation and fertile at the time so i took the pill the following day (monday).  i had no side effects. however, recently (friday) i was extremely dizzy and had a massive headache for about 2hrs. so i ate, relaxed and laid back for a minute and it was gone. so side effects can come days later. but hopefully like mine they are short lived. i still haven&#039;t gotten my period but it isn&#039;t due for a couple weeks."