Thanks for writing to H.C.M. for your query.
I have gone through your query regarding pain on swallowing even after one week of tonsillectomy
operation and a white slough is present over tonsillar area. Your son have now developed diarrhea
Considering all aspect of your complaints it appears as your son is having secondary infection over operated site otherwise usually after a week's time pain should not be so severe. Secondarly in postoperative period taking antibiotic for one week if there is suspition of secondary infection than there appears need for change of antibiotic, your son have developed diarrhea this again demands to think over present antibiotic.
Therefore it will be better for you to consult your surgeon for examination and further treatment.