Would a kidney infection cause a positve hcg in the blood?

I am about 10 days late for my period, i have takrn 6 hpt, all negative. I have had severe flank pain, went to er and diagnosed with probable kidney infection, although the hcg in my blood came out higher than normal.. it was a 5.51.. still negative on my urinel.. what could be going on??? calling dr tomorrow, but this seems like the longest memorial day weekend ever.. anyone help please!! oh by the way, i already have 4 kids, and cannot tell i i am on #5 or not!!!!