Hello.
Thank you for your query at DoctorSpring.com
Yes viral infections can be extremely annoying, if not treated properly stays for a long time, responsible for the kind of fatigue you're mentioning. From your initial symptoms, it seems more like a viral gastroenteritis, and it could have caused your fatigue. It happens mainly because of the dehydration.
The tickle down your throat seems to be an allergic manifestation. Have you ever been allergic to any kind of food? Even in food allergies you can have diarrhea, with the other allergy symptoms, and it can later manifest as malabsorption, can lead to fatigue. This is just a possibility. Try to see if there is some food item you have taken recently, or if something similar has also happened before, after a change in diet?
You said all your blood tests are normal. Did you get your hemoglobin checked? And your liver function test?
Since you had diarrhea again, i will advise some medicines. Please take them and let me know if you're improving :
1) Tab. Loperamide 1 SOS ( to control the frequency of diarrhea )
2) Tab. Ofloxacin- Ornidazole twice daily after food for 5 days. ( This will take care of both the stomach bug and parasite if any )
3) Probiotic capsules for a week. or supplements fortified with probiotics such as curd.
If your diarrhea persists, a stool examination for parasites and ova will be helpful. It will even be helpful in understanding if there is any malabsorption.
Hope this was helpful,
Regards.

Hello.
Thank you for the follow up.
Yes the ofloxacin-ornidazole will need prescription.
Kindly get it with the help of your local doctor.
Since everything else is normal, it points towards a gastroenteritis, you will recover once you finish the course.
Do let me know once you feel better,
Regards.