hi there, your unrelenting diarrhoea
could be due to a persistent stomach infection
or could be due to IBS
or intolerance to certain food items or could be more serious like malignancy of any part of GIT. you should proceed in the following manner. First of all you need your stool examined for routine and microscopy along with occult blood which will be able to guide whether there is any infection or underlying pathology, get an ultrasound
abdomen done to rule out any growth or any other pathology. Visit your physician who will be able to suggest any other tests required based on these test results. Take care.