How serious is a double kidney infection?

I had a uti about 2 weeks ago, and before that a kidney/bladder infection. Well now i have a double kidney infection and the bladder and uti is all cleared up apparently. I'm on strong meds to get rid of this one. But what are the damages these infections can do to my kidneys? Should I be getting checked for something more profound? Why do I keep getting them in the last little while? And how do I get rid of the awful awful pain?