What Causes Vibrating Sensation In The Rectum While Having COPD?

I have been having this vibrating sensation in the rectum that has been constantly occuring for the last few days. Maybe it s some type of spasm. I am 43 yrs. old and have has surgery to remove polyps 2x already over the last 4 yrs while having a coloscopy. I prevoosly had rectal bleeding starting in my late 30s. I am a pack a day smoker for 30 yrs and have COPD. I also had hemorrhoid banding last year but did not have the third vein treated yet. I do not currently have any rectal bleeding for many months now and have recently (last 4 days) started juicing, just one full cup a day. What can this be. It is not painful at all but constantly annoying.