You can start whenever you want, just know that you won't be considered protected against pregnancy for a full week. The "first day of your period" start is suggested so that the user is basically protected from the get go: really it's just that the "one week" time overlaps with the week during which you are least likely to ovulate anyway.
If you've already ovulated, you probably won't be able to skip your period. Plus, you may experience adjustment effects like spotting or PMS. They go away eventually, and not everyone gets those effects. But if you start right before your period, you're probably going to confuse your body and raise your chances of getting those effects.
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Date: 2011-12-30 11:03 pm (UTC)If you've already ovulated, you probably won't be able to skip your period. Plus, you may experience adjustment effects like spotting or PMS. They go away eventually, and not everyone gets those effects. But if you start right before your period, you're probably going to confuse your body and raise your chances of getting those effects.