Could i have picked up the bacteria causing my sepsis over a year ago? kidney stone last week, its stuck, admitted after second er visit for fever,

Probably longer: The bacteria that cause urinary tract infection -- with or without sepsis, kidney stone, etc -- are not caught from outside. Mostly they are entirely normal in the intestine, and it is likely you have carried the one that caused your sepsis in your intestinal tract for many years, perhaps your entire life. You'll probably never know for sure, and it probably doesn't matter.