What Causes The Mucus Discharge From Rectum During Periods

I have bright red blood when I wipe and a mucus from my rectum and this only happens when I am on my period. I do have a hemorrhoid, and had a colonoscopy done 5 years ago, I have had a large fibroid removed in December and utlra sounds before the removal of the fibroid with nothing but the fibroid showing up. What could it be?