Clearblue Test...WTF

Has anyone ever used this test, had a negative and was really pregnant? I am 7 days late no sign of AF and that chick is like clockwork and always on time. Last night I bought a test. First one came out with a book error...but I was in a shambles as kids and dog were in and out of the bathroom. I took another one about an hour later and it was negative. I have symptoms, but of course they are all that of possible AF too. Anyone??? I have my annual exam tomorrow anyways, bit this 3 week wait is killing me.