Post Nasal Drip?????

Since last night I've had a ticklish feeling in the back of my throat and I constantly swallowed saliva and the throat was irritated. I umed it was post nasal drip and took some anti-allergens. But since last night till today I still have this irritated throat, now it's sore every time I swallowed and all day today I've had a head ache (feverish-like) and my body felt really really weak. And I've taken some antibiotics just in case. Is it really post nasal drip? Or Have I got the flu or something?