Late af

Jessica • Hi I`m 26 years old, I have two daughter and we are trying for a third, we have been trying for about 6 months.
My last af was 12-18-14 glow said my af should have been here 1-23-15 today is now 1-29-15 and I have not had any signs of af showing up. I have taken three test and they all said negative. Could I be pregnant or just a really late af. I don't know what to do please help thanks