Am I pregnant? Or not?

Tee
Hi ladies! 
My period is 12 days late, but I still have a BFN. I've checked in with my dr and she said nothing is wrong, but I do have an enlarged uterus. Could this be causing my late period? I'm also experiencing lower abdominal (uterine area) fullness and bloating, I'm also fatigued, and have been having headaches the past few days. Anyone ever experienced this?