HI.
You have already complete the course of
Amoxicillin and
Metronidazole long ago and hence can not be correlated to any other the present problems of loose stools or mucus and need to visit bathroom on eating something.
This is indicative of either intolerance to some food and/or beverages or an intestinal infection.
I would advise you to go for stool tests on 3 consecutive days and see the result to have guided treatment.
Get started on an antibiotic, metronidazole,
probiotic, activated charcoal tablets.
Avoid all the foods and beverages which instigate or enhance your problems.
If there is no effect within 3 to 5 days,
consult a Gastroenterologist for clinical evaluation, examination,
colonoscopy and CT scan of the abdomen, to get a proper diagnosis and a plan for treatment.