i think i ovulated around the 24th or so.
I would ask your doctor for a blood test. That will tell you for sure. Good luck and keep us posted.
Do you know when you ovulated? It really depends on when you ovulate as to when to take a pregnancy test. If you know when you ovulated count 14 days from that date and that is around the time you should start your period. For instance, if you ovulated on Nov. 29, you should start around December 12th. You may have ovulated later this cycle which could by why you haven't started or as to why the pregnancy test is negative if you are pregnant.
I would test again, and if still - I would go and see your doc.