Brief Answer:
Acute gastroenteritis.

Detailed Answer:
Hello,
Thank you for trusting HealthcareMagic,

The symptoms you are describing are mostly suggestive of Bacterial gastroenteritis which is the bacterial infection of the intestine.Some times amoeba or particular species of e.coli called enterohaemorrhagic strain may be involved in it.They erode the soft mucosal layer hence cause mild bleeding.This blood may be there with stools.
Stool analysis and culture are required to confirm the diagnosis along with it stool for occult blood should be done to find out if it is actually blood or not.Darkness if tarry can be a indicator of upper gut bleed also.
Management as off now is with antibiotics (usually a combination of Ciprofloxacin and Metronidazole) for which you will need a prescription. So please be advised to follow up with the urgent care.

Meanwhile for letharge fatigue lassitude drink plenty of water and electrolyte containing drinks like Gatorade. Follow soft diet. BRAT (Banana, Rice, Applesauce, and Toast) diet will be easier on your tummy.Oral rehydration solution is available over the counter drink it.Diarrhea causes loss of sodium potassium and chloride ions which leads to extreme fatigue.The faster you would replete electrolytes the better would be recovery.

You can also take imodium 4 mg thrice daily to stop diarrhea.Its Over the counter.

Hope this answers your query
Please let me know if you need further clarification or details.
Follow up with reports and take medicines you would be fine in 3 days.
Regards and have a quick recovery.

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