Hello dear
I understand your concern
Dirhhea since 4 week is not norma.
It could be a chronic bacterial, protozoa infections, 
irritable bowel syndrome.
I advise you to consult the Gastroenterologist and undergo following tests,
test like CBC, ESR, Blood 
glucose, CRP, stool microscopy and culture.
maintain hydration and take rest.
Diet: rice, banana and 
ORS.
Take boiled rice with added lemon and salt.
doctor will prescribed drug according to cuase:
Tablet ciplox-oz wil helpful
Tablet vabact-DS
Soluble 
dietary fiber like senna.
Hope this may help you
Contact HCM for further Health query
Best regards
Dr. Sagar