alaysha is right, the urine test at the dr.'s would have been accurate at this point...Sounds like you may be bloated from PMS or something????
If you were pregnant you should of come up positive on a pregnancy test, especially if your period was due a couple of weeks ago. I would contact your doctor and see if they could possibly give you something to jump start your period. Also, you could try getting a blood test done to completely rule out pregnancy.