Hi..
Welcome to HEALTHCARE MAGIC..
As per your complain it does not seems to be bacterial infection or
strep throat, rather it seems to be due to viral infection leading to Influenza or flu..
Stomach discomfort can be a side effect of antibiotic amoxicillin that he has been given.
As it is a viral infection it will resolve once the virus will complete its cycle in human body..
As of now you can start with supportive treatment to relieve the symptoms like:
-Gargle with a warm saline solution that is by mixing 1 teaspoon salt in a glass of water and warm it to make a luke warm solution..
-Take a combination of decongestant like
Phenylephrine, mucolytic like Ambroxol and anti allergic levocetrizine and another combination of
Acetaminophen and Ibuprofen..
-Take cough expectorant containing Gueifenesin and cough suppressant containing
Dextromethorphan.
-Chew a Vitamin C pellet daily..
-Do steam inhalations..
-Avoid spicy and chilled foods..
-Sip on warm water throughout the day..
-Do warm compresses over chest..
Hopefully the symptoms will resolve within a week and if it worsen consult a General Physician and get evaluated..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.