Hun, you've taken HPT's and they are all negative...yes, it's possible you are pregnant and just too early to register on a HPT...this happens to many women.
As much as we would like to believe they are, our periods are NOT like clockwork. There are many many factors that can cause women to be late or skip a period altogether once in awhile.
None of us here are going to be able to tell you the "yes" or "no" that you are looking for. All you can do is wait for the blood test results.