If you already started the pills today, you definitely should not stop them. Just keep taking them one a day (at the same time every day) even if you start you period, or have some spotting or breakthrough bleeding, while still taking the active pills. Your cycle may be a little werid the first month or so, but then should even out and be normal by the third cycle.
However, if you have not yet taken a pill, you should probably wait to start them until sunday. By doing so, your cycle will suffer the least irregularity and you will likely have less spotting or breakthrough bleeding and have your period on time (during your placebo pills).
Just my two cents.