Could I be pregnant? 8 days late negative test

I'm 8 days late, I hd cramping the 1st 2 days of the days I should hv had AF. I've been having cramps on and off like AF since. I took a test at 3 days late and negative, I went to the doctor yesterday and I tested again and it was negative. He told me to wait 2 days and test again. He also gave me a referral for an ultrasound. I hv never missed a period and have never been late. I'm 36 and ttc my 1st, I also wonder if my hormones are staring to at up. Ur advice or similar experience is greatly appreciated.