Health concern

it could be from a lot of different factors. Maybe you have a allergy to some sort of pollen or something in the air,or maybe a certain type of animal hair. I get sore throat a lot when I swim a lot (from clorine in the pool) and also if my dogs have been on my bed - I then get a sore throat that lasts about a week or two. Also it could maybe be your tonsils if they aren’t removed.

About the anti biotics. A lot of times anti-biotics don’t work the first, 2nd or even third time and you have to have your doctor prescribe them maybe once again. I work in a pharmacy and many times people complain that they have been on 3 courses of antibiotics before their sore throats or whatever flu or infection they have stopped. So maybe you need to ask your doctor about it and let them prescribe it once more, or maybe a different type of antibiotic. Or go speak to someone who specialises in allergies etc.