Do all pregnancy tests detect early pregnancy?

My AF is due tomorrow....I've taken a few tests 2 being first response which I'm sure I did too early those were both neg, I also got a couple from the dollar store which I heard were pretty sensitive , I did one yesterday and today and both were still neg. I am also pretty crampy today I usually get cramps a few days before my AF, but they just started today.... Am I just being completely impatient or is that a good sign im not pregnant?