Re: kind of concerned....
If I were you, I would DEFINITELY be concerned. If you are using enemas or stimulant/laxatives together with stool softeners (I'm assuming that one or all of these were recommended/prescribed by your doctor), and are getting just some diarrhea with mucus as a result, then this COULD indicate a bowel obstruction. BE PERSISTENT with your doctor, or contact another GI specialist ASAP. NO RECTAL BLEEDING IS ACCEPTABLE unless you have a confirmed diagnosis of hemorrhoids.
I DON'T know how any doctor can tell you that the colonoscopy you had three years ago indicates a "low probability of colon cancer." You may not have had any polyps at the time of your last colonoscopy, but there ARE fast growing types of colorectal cancer, especially given the history with your mom. In other words, you could go in for a colonoscopy and have NO polyps present, and then develop polyps over a six month period which may or may not be cancerous. The statement makes no sense.
In any event, you SHOULD have another colonoscopy since you have had some bleeding, are over age 50, last had a colonoscopy more than two years ago, and most importantly, you have a family history of colon cancer!
Obviously, you need to resolve the blockage issue first... Drink PLENTY of water. Also, drinking WARM beverages like tea together with the use of a moist heating pad applied to your lower abdominal region can help to move things along. The fact that you are having so much mucus, together with diarrhea (especially if it is at all frothy in appearance) are symptoms of a blockage. You can also try some gentle massage in the tender area of your abdomen to try to stimulate your bowel to break the blockage.
PLEASE follow up with your physician/ER if you have ANY INTENSE, SHARP pains, and/or are running a fever. You may require surgery to re-sect the area where there appears to be an obstruction... which may have developed in the first place due to a polyp which has grown pretty large during the years since your last colonoscopy. I don't mean to alarm you... HOWEVER, this potentially COULD BE VERY SERIOUS, especially given your family history.
I wish you the BEST OF LUCK. Keep in touch.
ATTITUDE IS EVERYTHING!