When you take the tests are you using your very first morning, wakeup, urine? It is important to do so as it is more concentrated and will give an earlier result.
Did you notice any light spotting the week before your period was due?
Your symptoms are not specific to pregnancy. You could have a UTI as the symptoms also fit.
Retest if you need to or see your doctor. Sometimes, for whatever reason, the test just don't work on all women.