between periods could be due to ovulation, implantation bleeding during pregnancy, infection in an area of the body related to menstruation (including the vagina, the cervix and even the bladder).
syndrome, diseases of pituitary gland, hormonal imbalance of estrogen and progesterone and uterine abnormalities like fibroid and cervical dysplasia. Get your serum HCG levels done or do a highly sensitive urine for pregnancy test to clear the status of your pregnancy.
I hope it helps. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.