Hi, probably it is viral pharyngitis, please try betadine gargles along with anti histaminic (you are already taking one) and decongestants like pseudoephedrine. If no relief is seen in 3 days, get throat cuture done to rule out bacterial infection ( strep etc). Pain killers like ibuprofen might help too.
I forgot to write that I have allergies on flowers and I take disloratadin for that.