Is it possible the tests are false negatives?

I'm five days late for my period, and I've taken 4 over the counter pregnancy tests. One was Clear Blue, the other three were cheap ones. All were negative. Well, I've always been really regular with my periods, up until now. I'm even having symptoms like frequent urination, heightened sense of smell, nausea, and abdominal pain. Could these tests be wrong, or am I just REALLY late?