What causes intermittent occurrence of raspy throat?

I had an upper respiratory bug with laryngitis in January, followed by a cold a couple of weeks later. I still have what feels like a slight post nasal drip, but what s annoying is a raspy throat that comes and goes. It is better when I drink something or take throat losengers. My doctor said all glands and lymph nodes are normal so we tried an antihistamine nasal spray, but it doesnt seem to be helping. Any suggestions?