Welcome to just answer,
Thanks for answering my questions.
Now looking at your age,no history of unprotected sex,your symptoms,it seems that your diarrhea is from infectious cause as that may present with similar symptoms.Ask your physician to do stool for wbc,stool culture ,PCR for giardia ,stool for ova/parasites to rule out infectious causes.
Now there is a possibility that this could be due to malabsorption as you mentioned that you do have solid stools in between,so ask your physician to stool osmolarity,stool for fat to rule out malabsorption causes like celiac,whipple disease.
Now other possibility could be thyroid
problems as increase in thyroid hormone can cause resistant diarrhea,so ask your physician to do TSH to rule it out.
Now HIV can also present with diarrhea but as you mentioned that you do not have any history of unprotected sex so it is least likely,still you can ask your physician to do ELISA for hiv to rule this possibility.
Other possibility at your age seems less likely
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