[putting on my doctor hat]
Stress can be a significant contributor to physical symptoms, and digestive presentations are no exception.
The two things that give me pause are the fever and the the development of sympathetic symptoms among family members.
Without knowing your medical histories, it is not possible for me to know what might be happening, but it don't think that it is unreasonable to treat the symptoms (hydration and salts for diarrhoea, analegics for fever), as well as rest. If the fever continues for more than a couple of days, if there is blood, or if there is pain that is not associated with muscle cramps, then there maybe cause to do some further checking. (Though it sounds like your doctor is already undertaking a parasite screening)
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--James