More than likely you are not pregnant but i would not say that there isn't a possibility. my urine came up negative at the doctor when i was a few days late but my blood work came back as a positive.
I would go to the dr and have a bllod test just in case.
Its very common for a women to miss a period or for it too be delayed. Its so common in fact, that many doctors wont investigate the cause unless a women has missed 3 periods in a row.
You are not pregnant though.
Because no one here is a doctor, we couldn't tell you why it's late. There's ideas behind it, but no one could pinpoint it. It's possible you are pregnant, and the test just hasn't picked it up. You would do better to request blood work done at the doctors. They could measure the HCG and that would give a more accurate answer to if you are or not. If it still shows you're not, then they could work it out to see if there's a reason why you still haven't had a period.