What Causes Delayed Period And Sensitive Nipple While UPT Is Negative?

I am 29 years old and my husband and I have been trying and not trying to get pregnant for 7 years. I am currently 2 weeks late and my period is always on time! I have taken 2 tests and they came back negative so I waited a few more days and tried a digital test. It was flashing the hour glass thingy like it was supposed to and then it stopped and showed the manual sign. My breasts don't hurt real bad but are sensitive around the nipple, I have been having some cramping but it doesn't really hurt it's actually hard to explain for 3 weeks approx. I thought I had a bladder infection so I asked my doc to run my urine and it came back clean and this was before my missed period. Im just wondering if you think I could be pregnant or if I should call my doctor and set up an appointment. I was told that some woman don't show enough HcG levels in their urine to always be detecable in a OTC test.