absolutely certain I'm pregnant

I Am going out of my mind. I had my last proper period on the 17th of Nov 2010 and it is not the 28th of Dec at 2am. On the 9th I began having some strange spotting that was brown in the beginning and pink at the end and lasted for 3 days. I've never had a period less than 5 days long and Ive NEVER had spotting like that. I've taken countless urine tests and had a blood test on the 23rd of this month all of which were negative, however Im throwing up ALL the time, especially at night, have such sore breasts, lots of headaches, Im so tired all the time and I just feel so pregnant, but everythings negative. I've been so careful lately, eating right, not taking anything I shouldn't, taking folic acid every day. I just need to know whats going on. Im absolutely certain Im pregnant though, I just need some ideas about why my results are negative.