3 days late

I am currently 3 days late. I usually am very very regular with my 29 day cycle. I take my bbt regularly and use ovulation strips so I feel that I was pretty regular with my ovulation as well. I am still testing negative!! This is so frustrating. No period, no period cramps, no sore breasts, NOTHING like I get every single month. Is there still a chance I am pregnant and the test is just not picking up on the HCG hormones yet? This is my 4th month TTC. I am so anxious and ready for my 3rd baby!!!! It has been 6 years since I had my last baby!! Any thoughts??