Constipation can occur for many reasons. Dehydration, lack of fiber in the diet, some medications, nerve damage, etc. Hypothyroidism is a common cause that can also cause Depression and high cholesterol. Lab tests almost always miss hypothyroidism, so I recommend doing basal body temperature to check for hypothyroidism. Instructions can be easily found on the web.
Other than that there is not much information to go on. Nothing about your diet and water intake for example. Were you born premature, which could affect nerve development? Are the stools too hard to pass easily? Have you checked to see if constipation is a side effect of your medications?