Water & fiber. You should drink 8-10 full glasses of water each day, and more if you sweat during the day. Mild dehydration is under-appreciated as the cause of constipation. Next, make sure you increase your intake of natural fruit & vegetable fibers. If this still doesn't work, talk to you doctor about starting an over-the-counter stool softener or glycerin suppository. Rarely intestinal tumors cause this.