there are many factors for the occurrence of constipation.
I suggest you eat a lot of Fibrous Foods.(e.g. whole wheat breads, legumes,prunes and nuts)
don't forget to do regular exercise. Sometimes, lack of exercise lessen the gastric motility and digestion.
And lastly, drink a lot of water. At least 2-3L/day.
Happy eating!^_^

"I don't go back on my words, that's my way of ninja"