My body can't digest a lot of food at one time. it takes days. could there be an intestinal blockage?

Likely constipation: It actually sounds like your constipated and not a blockage. It should not take days for food to pass through your body. Usually it should only take about a day. For constipation I would advise you first increase your fluid intake. Maybe around 3-4 glasses of water. Then increase your fiber content. Look for cereals that have a high fiber content. Fiber one has 14 g of fiber in one bowl.