Hi, Welcome to healthcare magic community forum..
Birth control pills, though the best contraceptive
method, are not 100% effective. They are known to have failure rates of 10-20%. Hence pregnancy
is a possibility, if your periods haven't started yet. Get an urine pregnancy test or blood HCG
levels checked. If they are negative, then other possible causes have to be considered, not before confirming pregnancy
with a repeat test after an week..