Should I expect my untreated allergies to always go into a sinus infection, if left untreated?

For a few years, now, and usually twice or three times each year, I suffer what has seemed to be odd sinus or upper respiratory infections. They always start the same way. First, it's the scratchy throat and the feeling that I have mucus in my windpipe that causes me to clear my throat repeatedly. From there, I begin to notice sinus headaches, a general unwell and fatigued feeling, and then the cough that comes with it some very foul-tasting thick, sticky phlegm that is difficult to expel from the lungs. Once the cough gets underway, my throat and ears become extremely sore, keeping me awake at night, along with a very annoying dry, hacky cough, also, which contributes to my staying awake much of the night. From there, it usually spreads to my sinuses, causing me to sneeze quite a lot and expel thick, yellow mucus when blowing my nose, as well. The only thing not present when all this madness is going on is a fever. I never have a fever at all during all this. Nevertheless, I always take myself back into the same ear, nose, and throat specialist who puts me on an antibiotic, specifically Augmentin for ten days, accompanied by something like Xyzal, which is a daily allergy pill. Anyway, I always get better as each symptom goes away, one by one, until eventually I'm back to normal. A few months p, we enter a new season, (in the state I'm from), and wham! I'm back to the new-symptom-every-day-thing until I'm sick enough again to go back to my ENT doctor yet again. My question is this: Why is this so-called "sinus infection/upper respiratory infection" coming on always in the spring and always in the fall? It seems I stay pretty good in the summer and in the winter, but never spring or fall. Here's the second question: Do seasonal allergies behave this way? Is there a chance that lots of allergens are entering my airway from weeds, trees, pollen, mold, etc., and since I've never been tested for allergies, these allergens just "build up" in my airway, so the mucus increases to protect my airway from these allergens, and then all the increased mucus that is created is then a haven for bacteria to suddenly begin to settle and colonize, thereby making me sick with what seems and feels like a sinus/upper respiratory infection? I just don't know what to do. I'm tired of feeling fatigued, itchy-eyed, run-down, and just "not normal" so much of the time. Can allergies really cause a person to feel this lousy? Anyone with previous dealings with allergies or chronic upper respiratory infections please feel free to respond to my questions. I'm at my wit's end with this. I'm a mother of two small children, and I just really don't have time to feel bad so often. I would think my ENT doctor would have more input/information/answers, but I have yet to come to any conclusion. Thank you!