My constipation stopped when I eliminated gluten 7 years ago. You should also take digestive enzymes with your main (big) meal. You may have low stomach (HCL) acid - you could research that but I can tell you b6 and zinc are required to make stomach acid. (these are deficient in pyroluria by the way). Look at copper toxicity too.
do you do light exercise? walking, swimming? Luckily digestion for me is one area that has continually improved over the years and rarely troubles me so maybe you have some issues I did