The ultrasound was probably more for the purpose of looking for any sort of abnormalities with the structure or flow of your kineys, ureters, and bladder. Swelling, blockage, or inflammation would show up, but not the bacteria itself. Normal is good, but doesn't rule out infection, if that makes sense.
Usually when an infection reaches the kidneys, you'll have back pain specifically in your lower back around the very bottom of your ribcage, where your kidneys are, you'll likely run a high fever (kidneys help to regulate body temp), and your urinalysis will show protein, as well as a few other possible things (like red and white blood cells, and nitrites) that a bladder infections would show, but in larger numbers.
The antibiotics alone won't ease your symptoms, they only kill the bacteria (once the infection is completely gone, your symptoms will go away). You can ask your doctor for a prescription called pyridium, which will ease the symptoms in the meantime. It will turn your urine a dark orange color, so don't panic if you see that. You can also look for
AZO Standard over the counter, which will also help if you can't get the Rx.
Hope that helps a little, and hope you're feeling better soon.
