You have lower back pain
with bleeding p/v or p/rectum
its not clear , if you are a female than consult your gynecologist or if you are male than consult your surgeon or oncologist
and go for ultra sonography
or CT lower abdomen immediately to rule out any possibilities of any malignancy of lower abdomen uterus ,ovary or cervix or rectum.
Hoping you will take care immediately, good luck.