Since you suffer from chronic constipation you should see your physician or a gstroenterologist to get examined for fecal impaction and to get throughly examined for the underlying case for your constipation problem.
People with chronic constipation may develop a fecal impaction, that is a hard, dry mass of feces located in the rectum, with symptoms of abdominal cramping, small, semi-formed stool and sudden watery diarrhea (liquid from the upper gut portion that could pass through the impacted stool at the rectum).
There are various causes for constipation like neurological diseases, mental conditions, drugs side effect, hormonal disorders, or functional bowel diseases.
Colonoscopy should be performed in order to check for colon cancer.

Best wishes!
Marija