What Causes Prolonged Bleeding Along With Vaginal Clots?

after done my breast cancer my priods started after 8 months every month but lasts for a month with clotting.starts slowly for a week then becomes heavy lasts for 17 or 18 days then get slower age is 46 doctor told me in the beginning afterbiopsy (4yrs back) it is hormonal imbalance I am having rt now also from the last3 weeks do not know when it will stop suggest me something even me and my husband is fed up of this thankyou/