Five years ago i had . last year i had 2 blockages resulting in bowel resection. since then i have anal discharge after most bms & constipation often.

Probably mucous: Mucous is a natural lubricant produced by the colon when you are constipated. So i suspect your constipation is the culprit. It is not uncommon to have a change in bowel habits after abdominal surgery. I would suggest you try some daily stool softener or mom for a few weeks, enough that your constipation is gone, and see if the mucous disappears as well. That will cinch the diagnosis.