Suggest Treatment For Throat Infection

Question: Hi,
I am XXXX and currently 29 Years old.My problem is with throat infection .All this started 3-4 years back and since then I get throat infection every 15-20 Days . Its effecting my daily life all the time I am felling feverish and tired. When I get this ,it usually stays for 15 days. I tried everything some doctors said it could be because of sinus ,some said it is because of allergy .Had every Antibiotic available in market from amoxicillin to azithromycin and many more . Also anti allergic. However i used to get sick in childhood also due to Tonsillitis, but that stopped when I was around 15-16 Years old. I have gone through many tests also like throat swap and all but no results .
Now I want to know how this can be cured and what medicine I should use. This is just that my immune system is week or its just pure allergic behavior of my body. For past some time I have stopped taking medicine and just do gargles and only goes to antibiotics when I get too much fever or it stays for too long.

Hope to get a satisfactory response from you .

Thanks,
XXXX XXXXXXX

Thanks for your response !!

I have never gone through these tests , however did throat swap and X-RAY for Sinuses and that was fine.

If these tests are necessary please tell me where I can get these tests and how much they will cost me .

I hope you can understand my situation , I am not able to live my normal life and always feeling sick .
I have seen so many doctors but not getting cured this is also giving me stress and depression.

Thanks,