5 year old diarrhoea for 3 weeks. Advice?

Hi everyone so my 5 year old has had onoff diarrhoea for just over 3 weeks. Its like one day off two days on and repeat.. hes had majority time off school due to it.

Hes well in himself tho and the gp wont do anything until its been more than 4 weeks.. anyone else experienced this?