Thanks for writing to us with your health concern.
If your period stops before your placebo pills are done, you still take the rest of the pills.
do not discard any pills.
Continue with the sequence of the pills irrespective of the day your period starts.
also, as this is your first month of pill use, make sure you use a back up protection method, as it takes a month for birth control to become effective, if you are using it for contraceptive
all the best.