I just a urine test done and it showed blood and large leukocytes. i also have been having lower right back pain what could this be?

Stone?: This could be a pyelonephritis (a kidney infection) especially if you are having fever/chills. It could also be a kidney stone. Perhaps a less likely possibility is a contaminated urine specimen (skin cells during collection could give impression of UTI) and an unrelated cause of low back pain. Presumably since you've had a urinalysis you've sought evaluation. If not, you should do so.