relax and wait. I got UTI's all the time and took Macrobid for infections and my periods would always be late (they were usually unpredictable *anyway* not necessarily because of the UTI/Macrobid tho).
8 tests in 7 days tells me you're stressing! So, relax, wait until Day 10 or even Day 15 then test again if you still haven't gotten your period. Chances are you'll get it (if you haven't already)