Diarrhoea during pregnancy

Hi All, Just back from oversea few days back and start having bad diarrhoea for four days already eaten charcoal pill and went to the hospital for a check as feeling very unwell and having bad stomache. However during pregnancy not much medicine can be prescribed. How long would the diarrhoea go off? Currently 16 weeks +. What the fast way to stop the diarrhoea?