I think you have received very good advice so far.
While it can be tough to continually deal with sickness now, you will be wholly thankful when these illnesses will mean days missed from school. I know that's no comfort, but I wanted to reiterate that point.
Secondly, I 100% agree with all the other posts about antibiotics. I am, frankly, very surprised your doctor is prescribing so frequently. My son at 17 months has had a couple colds, nothing too major, but has never had antibiotics. Our Ped. doesn't even prescribe antibiotics for ear infections unless it is prolonged. Studies show that most ear infections resolve without meds, and not prescribing can definitely get you one step further away from having resistance to meds, when you REALLY need them.
You will want to keep an eye on her definitely, but I wouldn't run to the doc just yet. If she sounds wheezy, or has an overly productive cough that she gags on, maybe something like benedryl or a prescription med for that single symptom would be beneficial. My daughter has had pnuemonia 3 times, and I always knew when her bronchitis-like cold slipped into pnuemonia because she would start vomiting several days after showing symptoms.
If anything, ask the doc for something to help treat her symptoms, if they're severe (like benedryl, to help dry her up a bit for nightime so she can sleep. It is also entirely possible that her symptoms are aggravated by the very high pollen count right now...and she may very well have allergies... and... she could be teething - all of which are bound to cause the symptoms you describe.
I also agree with other posts about using PROBIOTICS - whatever form you choose, they are so very beneficial in helping your body fight infections... they can even be taken with antibiotics... I take them to prevent yeast infections post antibiotic use.
I hope that your little girl finds a little break from feeling yucky...