Doctors don't usually take constipation seriously, but people who have constipation usually do. The best definition of constipation is not defecating often enough to feel comfortable, whether that is three times a week or three times a day. If you don't feel good, then there are things you can do to relieve the problem.
Constipation is primarily a problem of hard, tight, dry stools. The solution is to make sure stools are moister and bulkier so bowel movement is easier. Part of the solution to any case of constipation is drinking enough water—8 glasses of 16 oz or 480 ml each is not too much.
Another part of relieving constipation is making sure that your gut has a steady supply of probiotic bacteria. These friendly bacteria not only break down fibers that human digestive enzymes cannot, they also make up about 1/3 of the volume of fecal material. If you don't have probiotic bacteria in your small intestine and colon, your stools will be small, hard, and difficult to pass.
If you don't have the probiotic bacteria in your gut first, then fiber will tend to clump in your gut. That's why you take a probiotic before you start making sure you eat more high-fiber salads (radicchio is a favorite food of probiotic bacteria, as are sunchokes/Jerusalem artichokes, bananas, asparagus, and chicory) and green vegetables, such as cabbage, broccoli, and the often-villified Brussels sprouts. Take the dosage of probiotic supplement, such as Nexabiotic 20-Strain Multi-Probiotic Supplement, recommended on the label for 2 days, and then start adding high-fiber foods to your diet. Just eat 1 or 2 servings of vegetables the first few days while your system is getting used to them, and then work up to 5 a day or more.
Really need to go? Even Og and Thag could have taken Epsom salts, which naturally occur in nature. Even better, reach for MOM, Milk of Magnesia. Either product, taken as directed, draws water into the lumen, the central cavity, of the gut, moistening and softening stool, making bowel movement easier. And both products provide magnesium, which is healthy for the heart and central nervous system.