Here is what I have been dealing with...
I am currently 10 days late. I have had extreme fatigue since the 7th or 8th, and all of my pregnancy tests came back negative. I spent yesterday morning throwing up and had diarhea. Today, I went in for a sonogram of my breasts b/c one of them has a massive lump on it that just popped up last week.
Well, the doc said that it was just dense new breast tissue, and tonight, I finally had what I am pretty sure is a possitive preg. test. It was the faintest line, but the line is there. So, I'd say keep testing if you want to. It took me 10days AFTER my period was supposed to start to find out! And this will (hopefully) be my 3rd pregnancy and I've never been this late before. :)
Good luck dear!