Chronic pharyngitis or Allergy?

About a month ago, I began to notice a slight nasal congestion and coughing (felt like something was caught in my throat) similar to the usual symptoms of the flue/cold, and just wrote it off as that. In a couple days, it went away. However, another day or two went by, and the same symptoms came back. This has now become a pattern for the last month, with the symptoms becoming more severe. My nose is constantly running, and/or I'm coughing so much that I can't sleep at night and at times causes me to choke up and barf and a white-clear foam (doesn't seem like mucus or phlegm) comes up when I cough. I've also noticed a slight fever during these "episodes". I've managed to supress it enough to sleep with a couple tylenols/over the counter pain medicine during the times it gets very harsh, but since the symptoms keep reaccuring, I'm sure this is only a temporary solution. During the last couple months, I have not changed anything in my surroundings or changed my diet, and my daily regime has been the same also, but I can't help but think that this is a new allery or an allergy I didn't know I had until now..? What else would cause this?