M.M.
Hi A.,
It may be some kind of stomach bug that's going around, because my two year old and my boyfriends three year old have had the explosive diarrhea thing for about three days now. Nothing else seems to be wrong with them and they are happy and don't seem to be sick in any other way. My son did throw up once after eating his vitamins one morning, but immediately went on to playing afterward and just said that he had a little tummy ache. Anyhow, maybe it's just a little tummy bug. As long as she stays hydrated and seems happy it should probably pass, but 3 weeks does seem like a long time.........I think I would take the advice of the woman who suggested doing a stool sample. Good Luck!