Main causes of spotting between periods
could be due to pregnancy, birth
control pills, infection in an area of the body related to menstruation
(including the vagina, the cervix and even the bladder). Other causes could be polycystic ovarian syndrome, diseases of pituitary gland, hormonal im
balance of estrogen and progesterone and uterine abnormalities like fibroid and cervical dysplasia.
In your case, it can be due to the birth
control pills. Stop the pills and see if it persists.