13 days late, and negative HPT's?

First off let me start by saying that my spouse and I are currently trying for baby number 1 (I’M SO EXCITED). Well the first day of my last period was February 21, 2009 and ended the 24th (4 days) which now makes me 13 days passed my missed period for March. I took an HPT on the 4th and 5th day of my missed period but of course they were negative. I went to my OBGYN on the 6th day and had a blood test done (still waiting on my results, I don’t know whats going on with that!). I finally broke down and took two more HPT’s on the 31st and the 1st…still negative. Before my period was actually due I had back pain which has just now here in the past few days gone away. My nipples started getting sore a few days after my period was due, and then a few days following that the whole breast began to get sore. They seem to be getting more sore by the day. My spouse says that my nipples look like they’re are almost turning like a purple color and my areola’s are getting wider. He has also pointed out the veins that are darker and running through my areola and breast. So my question is, is my body just playing mean tricks or is there still a chance that I could be pregnant? If I were to be pregnant, then I should be a little over 5 weeks.