if you used the pills as per the schedule without missing even a single pill then there is chance for complete protection,
while on pills menstrual irregularities like amenorrhea
, delayed periods etc are common,
your symptoms may be side effects of pills,
anyhow as there is around 1% failure rate for pills better to undergo blood test
once which will rule out the possibility,
if comes negative you can continue the pills as usual, if comes positive you can decide what to do next after taking your doctor's opinion.