Thanks for writing to H.C.M. for your query.
I have gone through your query regarding itchy and painful throat. As you said initially you were having only itching in your throat and your doctor had given you montelaukast and cetrizine
which had relieved your itching but from next day you developed severe pain
Considering your clinical history it is clear that initially you were having allergic pharyngitis
which later on aquared superadded infection and now it is acute pharyngitis
.Here you feel difficulty in swallowing as well.
As far as treatment is concern you should take antibiotic, anti inflammatory, anti allergic and decongestant. You may take warm saline gargling also.
I hope you will be benifitted by above treatment and you will recover soon.