Could recurrence of nasal sinus congestion with thick mucous secretion be due to nasal polyp?

Hello doctor,

Approximately one year ago, I began to have recurrent, once per month or few weeks approximately, left-sided sinus congestion. Though my nose was never stuffy, I could feel the congestion somewhere between my lower nasal passage and sinus. When I would go to clear this, it would take a few minutes of hard blowing to get it loose enough to exit. When it finally would clear, the mucous was the strongest, thickest, non-separating gelatin-like, clear or white material I have ever come across. I chalked it up as allergies as I have begin to develop them mildly at the age of 40. This symptom over the last six months became more frequent, and now, for the last week, it is there daily and bright, dark yellow. The mucous is still very difficult to bring out, and sometimes I am able to bring it through the oral cavity, after incredulous amounts of effort. The mucous is so sticky it wants to stay right where it is. Or could this be a polyp issue, possibly? It is symptomatic of sinusitis as it is an obvious infection, but I am not stuffy at all. I can breathe finely. No fever or other symptoms, aside from very slight sinus pressure, but I sound nasal when I speak like I have a cold.