Spotting and continued mensuration.

I had my periods on 20th Nov 18 and is continuing till today ie 18 Dec 18. The flow started with spotting then very low flow in brownish colour . At present the flow is still low and dark red to brown . I feel no pain but only itching  due wearing pad on outside surface. I had low heamoglobin in September month for whichi had taken medication of iron tablet and heamoglobin raised from 5.6 to 10. At present my heamoglobin is 10.28. I have never missed a period. After marriage on Feb 2018my diet changed from non veg to veg. And I have also gained weight. I was always on bulky side of weight till now. I have consulted a doc but after all the blood test came normal Nd ultrasound of ovary and blader came normal. She said nothing happened and no other explaination on abnormal long and low flow of mensuration.