Lung noise turned from wheezing to crackling?

If your fever is going down, that is a good indication that your lung infection is getting better. Without actually listening to all parts of your lungs myself with a stethoscope, it would be impossible for me to know if you had bronchitis (an infection of the lining of the breathing tubes in your lungs) or pneumonia (an infection of the actual lung tissue). From your doctor's choice of antibiotic, I suspect your doctor felt you had bronchitis. I would keep taking the antibiotics, and if you're not significantly better in another 3 or 4 days, call your primary doctor (no need for another ER visit). If your breathing problems get significantly worse (worsening shortness of breath) in the meantime, then by all means go to the ER.