I don't usually get utis. is it unusual to suddenly develop pyelonephritis and is there anything i can do to prevent it in the future?

Pyelonephritis (kidney infection) occurs in only a small proportion of UTIs, but isn't rare. It's usually random with no means of prevention, but recurrent pyelonephritis is uncommon. However, some cases result because of anatomic problems like kidney stone or other problems. If you have pyelo a second time, diagnostic tests (like CT scan) should be done. Discuss with your doctor. Good luck.