If your constipation continues for a more than a couple of weeks, I would say it may be worthwhile paying a visit to the doctor to check that it is not a symptom of anything more serious.
However in the meantime there are lots of natural ways to attack the problem yourself to see if it clears up without medical intervention.
Fibre: the key to healthy bowels, and to keeping them moving, is to eat a diet which is high in fibre.
You can get fibre from a number of different sources, such as fruit and vegetables, beans, bulghur wheat and cereals that are high in bran, such as Bran Flakes and All Bran and porridge oats.
Water: if you are constipated it is very important that you do not get dehydrated as your body will absorb the water from your bowels which will make it even more difficult to keep things moving.
Finally, you may want to try over the counter laxatives, or mints and coffee, as these can sometimes help too.