Can uti symptoms come and go? Kidney infection?? Please help!

So about since December I've have on again, off again uti symptoms. Painful burning urination, then lots of pain following for several hours later. Then it'd go away completely for a few weeks. Then return. Finally I went to the doctor and my immediate urine test came out negative but when they sent the urine culture to a lab it came back positive. So they have me on what they think to be ineffective antibiotics and they want me to wait 4 weeks to see if the antibiotic worked or not. Well, while lying in bed, I got a sharp, sudden, shooting pain in my right flank area of my back where my kidney is. I've also been experiencing lots of abdominal cramping and nausea so I'm not sure what's going on but I'm truly worried about this and I don't want to wait another 4 weeks if I have a raging kidney infection going on. Please help! Anyone have any experience with this?? Thanks in advance!