Dark brown spots on the roof of mouth are petechial spots.Fever, sore throat
and dark spots on palate all are suggestive of Infectious mononucleosis
a type of viral infection. Amoxycillin
intake in infectious mononucleosis may precipitate the rashes. This is an infectious condition and can spread from one family member to others.
I would suggest you to consult your physician for laboratory evaluation( like complete blood count
, liver function test, antibody test) for making a diagnosis.
Antibiotics have no role in management. Give plenty of water to maintain hydration, paracetamol
to control fever, warm saline gargle and complete bed rest. IM resolves spontaneously within days to weeks.