Brewer's Yeast
I too had some problems at one time with irregularity. I noticed when I started taking brewer's yeast tablets (not really the same thing as nutritional yeast), I started being more regular. I also find that eating salads and other greens helps keep me in balance. Apparently, a huge number of people who eat Western diets, have depleted levels of the B vitamins and certain other things that are abundant in their natural form in brewer's yeast. It has also boosted my energy level considerably and made my skin more youthful. I take six to ten tablets every day. Eating sweets, or any foods with processed sugar (as opposed to naturally occurring sugar) in it, tends to destroy the B vitamins in your intestinal track and they are needed for optimal digestion and intestinal health. I also take cod liver oil capsules and I feel that they also help.
Good luck!