Nausea, Back Pain, Loose Bowels, Cannot Eat Much.
Thanks for posting your query.
Nausea and loose stools do indicate a gastroenteritis either viral, or bacterial.
The cause if viral, then it should subside on its own within a week, but supportive treatment with oral rehydration solution and probiotics may decrease the complications like dehydration and hasten recovery.
If you develop any new symptom like fever, blood in stools or vomit, abdominal cramps etc it would be more likely a bacterial gastroenteritis.
In that case you should consult your physician or gastroenterologist to confirm the diagnosis with investigations if needed( stool test, complete blood count etc) and start appropriate antibiotic course.
The lower back pain may or may not be an associated finding and may respond to antispasmodic analgesics like dicylomine.
Please consult your doctor if your intake is poor to prevent complications like malnutrition and dehydration.
Meanwhile do drink plenty of water and other fluids or take sips of oral rehydration
solution. Your appetite may take a couple of days to improve.
Hope I have answered your query. Please write back if you have further queries.
Wishing you speedy recovery.
Regards.