I took a pregnancy test on the eight of this month it was negative my period was due for the ninth of this month because I had it the ninth to the thirteen on last month my period still haven't come yet and today is the fifteen... what's wrong?

Probibly nothing... if you are only a few days late NOW... you have to wait at least another 2 or 3 WEEKS to take a test that has a chance of giving a remotely accurate answer... 4 weeks more if you want one you can be sure about.

You are testing WAY, WAY too early to get a remotely accurate result.