The problems you have mentioned as a contraindications for lactifibre like intestinal obstruction
, fecal impaction
, colonic atony are very distressing problems, they will make you feel sick and you would have been probably got hospitalised in 2-3 days if you had them.
So I think you have chronic constipation
lactifibre group drugs are called bulk laxatives because the absorb water and form bulky soft stools, that moved the rectum
Obviously you need more water intake for these drugs to be effective.
Because they are bulk laxative so any mechanical obstruction must be ruled out before starting them.