You have not mentioned your menstrual dates, so I hope you did not take the pregnancy
test soon enough
Irregular bleeding is very common while on oral contraceptive pills
SInce your history is not clear, please consult your health care provider to rule out a pregnancy/ other causes of such irregular bleeding.
It could be due to pregnancy, hormonal
effects of pills or stress, anxiety, thyroid
hormone dysfunction, some cervical lesion etc.