Sore throat, ++ redness/ulcers up back/roof mouth. dr gave amox- vomiting &diarrhoea- started shortly after dr. 2 days post anti no change- thoughts?

Diagnosis: Clearly, without seeing you it is impossible to arrive at an accurate diagnosis. It sounds as if you have a viral infection, possibly due to a coxsackie virus causing herpangina, and the vomiting and diarrhea, either part of the viral infection or a reaction (several possible) to the antibiotic. Ask the doctor whether they tested for strep and the results. If negative, stop amoxicillin.