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You should consider visiting Gastroenterlogist for complete workup.Chronic diarrhoea or constipation
are most commonly due to chronic Giardiasis
, IBS , immunodeficiency
, malabsorption syndrome
So it is important for you to get evaluated properly.You probably have malabsorption and so weakness due to deficiency of proteins or vitamins or fats.
If you need more information feel free to mail me.