I Had A Bowel Resection To Include A Sigmoidectomy With

I had a bowel resection to include a sigmoidectomy with colostomy for colon cancer, also had to have uterus and tubes removed as well, now 4 months after surgery I have what I think is a dark discharge vaginally and a lot of lower back pain, the discharge is dark enough to stain underwear badly and I have had increased pain in those areas???