hi mr ..your symptoms of lower back pain
, blood in urine suggest that ur suffering frm renal calculi
...as ther isnt fever as such dnt get worried of kidney infection
and yes ther is a chance that u may get infection if renal calculi is not attended in early stage...go consulta urologist
,get a usg abdomen done nd x ray kub..investigations reveal the location nd size of the stone if at all the scan is positive...