My Last Period's Start Date Was October 24th And It

My last period's start date was October 24th and it is now December 1st and I have not yet started. My periods have always been irregular, but always early and not late. I have taken two pregnancy test both came back negative. Could I be pregnant? I am having lower back pain, nauseas, bloating, and I have been really tired in the last two weeks or so. I did have about a half a day of some light spotting a few weeks ago. Please help, it is driving me crazy.