Serious Question...

So, the past few days, I've noticed that my breasts are really sore- Specifically around my nipples, and they're really hard too. I read that it's a sign of pregnancy. I'm currently in my fertile week. AF isn't due for another week or two. I took a test earlier tonight and got a BFN. I know this might sound like a really stupid question, but could I be so newly pregnant that it's not showing up on the test yet? Am I better off waiting to see if I'm late before testing again?