Constipation is often a sign of insufficient hydrochloric acid (HCL)in the stomach to digest the foods eaten. HCL production is a para-sympathetic response, which means we need to be fairly relaxed for our stomachs to produce it properly. If we are stressed, our digestion is impaired. We also need to be sufficiently hydrated to produce the HCL as well. Food combining and food quantity is also important. You don't want to put out the digestive fire.
Taking sour fermented foods, such as yoghurt, kefir, real sauerkraut etc, or some carminative herbs and spices (like ginger, cumin, coriander, fennel,pepper) with meals can help stimulate digestion. Or you could try taking some digestive enzymes with your meals.