Late period, negative tests...

Kate
Hey! I'm confused I guess. I have been off the pill for 2 years. My husband had a vasectomy reversal the first week of October, and we have been trying ever since. I have been pretty regular, with 30 day cycle's. I was due for my period on January 3rd. I took a test on December 31 that was negative. My period did not come on the 3rd as expected. I took another test on the 6th that was also negative. It's now the 9th and I have still yet to receive my period... I'm not under much stress, and can't think of any other reason to be this late. My  husband works at a local hospital, and I have been using the hospital grade urine test. Should I try another brand?
I don't know... thoughts..?