Black blood is dead, I would be REALLY worried if it was very bright red or appears fresh, that is bad. It must be a lining somewhere...Though I would still get the opinion of a Healthcare Proffesional. Oh and also, I would advise to cut down on the douching, it can dry you out down there.
Hello,
Given your history of cervical cancer and now having dark brown blood, it is advisable to seek an appointment with your gynecologist and get the status of your cervix evaluated. You may need colposcopy and endocervical curettage.
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.