Thanks for your question on HCM.
I can understand your situation and problem.
By your history and description, in my opinion you are having mostly upper
respiratory tract infection (URTI).
It is mostly viral infection.
And treatment is symptomatic only because it is self limiting.
Antibiotics are given to prevent secondary bacterial infection.
So no harm in taking flucloxacillin.
Along with this you need to follow these for better symptomatic relief.
1. Avoid oily and spicy food.
2. Avoid hard to chew food.
3. Drink plenty of fluids orally and keep yourself hydrated.
4. Start antihistamines and anti inflammatory drugs.
5. Warm water gargles 5-6 times a day.
You will mostly improve by 5 - 6 days.