A.E.
When I was pregnant with my son I took a test one week and it was negative, a week later it was positive. When I went to my OB a few days after the positive result, the ultrasound showed that I was already 7-8 weeks pregnant. The home tests say they can tell as early as 10 days, but they don't tell you that you have to have a specific level of HCG for it to be positive and some women don't reach that level until weeks later. So if you're not producing enough HCG yet, you will get a false negative. I'd call my OB and set up a blood test. It's the most accurate way to tell. However, even a blood test can be negative. If you're egg has not attached to your uterine wall yet, then no HCG is being produced so there would be no positive results until that time.
And believe me, I know how you feel. I've been having some obvious pregnancy symptoms recently, and have been since the middle of April, and I'm still getting negatives too.