lining (old menstrual blood) or an oncoming early period. That is the reason perhaps it comes periodically. But you should check up with a gynaecologist to rule out any vaginal
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.